Variations In Hypoxia Research Articles

Abstract SY31-02: Determinants of hypoxia in pancreatic cancer and identification of ULK1 as a potential therapeutic target

Abstract The effectiveness of radiation treatment is impacted by spatially defined features of the tumor microenvironment including areas of tumor hypoxia. This is due in part to direct protection against radiation damage by hypoxia, as well as through the influence of hypoxia on tumor, stroma and immune cell phenotypes. Despite this understanding, our progress in advancing therapies to address tumor hypoxia in patients have been largely unsuccessful. This is driven in part to the incredible variability in tumor hypoxia across patients as well as to a limited understanding of the underlying causes and consequences of hypoxia on an individual patient basis. As a step towards more precision approaches for hypoxia directed therapies we are characterizing hypoxia and its causes in individual patients and in matched patient derived xenografts. Our data reveal a striking variation in hypoxia across patients, and a corresponding variation in both oxygen consumption and hypoxia tolerance in patient derived organoids. We hypothesize that levels of hypoxia within individual tumors are determined through separate processes that drive changes in oxygen demand coupled with those that influence adaptation and survival to hypoxic stress. We have also identified ULK1 as a key contributor to both of these processes. Loss or inhibition of ULK1, a gene activated downstream of the unfolded protein response during hypoxia, results in defects in both mitochondrial and ER turnover leading to increases in both oxygen consumption and ER stress. Consequently, knockdown of ULK1 in established pancreatic cancer xenografts results in development of more hypoxia, while at the same time promotes the death of cells that become hypoxic. This has a dramatic impact on tumor growth, leading to complete remission in some models and suggesting that ULK1 should be pursued as a tumor microenvironment therapeutic target. Citation Format: Ji Zhang, Dan Cojocari, Rob Cairns, Marianne Koritzinsky, Bradly G. Wouters. Determinants of hypoxia in pancreatic cancer and identification of ULK1 as a potential therapeutic target. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr SY31-02.

Effect of 3D printed polycaprolactone scaffold with a bionic structure on the early stage of fat grafting

Mature adipocytes are sensitive to stress and hypoxia, which are the two major obstacles in large-volume fat grafting. Bionic scaffolds are considered beneficial for fat grafting; however, their mechanism is still unclear. In this study, polycaprolactone scaffolds were fabricated by a 3D-printing technique and compounded with liposuction fat. They were implanted subcutaneously into nude mice. At different times, gross and histological observations were performed to evaluate the retention rates and histological morphologies. Adipocyte viability, apoptosis, and vascularization were analyzed by special immunostaining. Quantitative polymerase chain reaction was used to detect the variations in hypoxia and inflammation. The results showed that the volume and weight retentions in the scaffold group were higher than those in the fat group with the former exhibiting fewer vacuoles and less fibrosis. In immunostaining, elevated CD31+ capillaries, more perilipin+ adipocytes, and fewer TUNEL+ apoptotic cells were observed in the scaffold group by week 4. The lower expression of HIF-1α indicated the alleviation of hypoxia. In conclusion, the scaffold provided mechanical support to resist skin tension, thereby decreasing the interstitial pressure, and improving substance exchange and vascular ingrowth. In this regard, the scaffold attenuated hypoxia and promoted vascularization, making it a feasible method to increase long-term retention in fat grafting using scaffolds with suitable degradation rates and additional vascular maturation stimulation.

Hypoxia and perfusion in breast cancer: simultaneous assessment using PET/MR imaging

ObjectivesHypoxia is associated with poor prognosis and treatment resistance in breast cancer. However, the temporally variant nature of hypoxia can complicate interpretation of imaging findings. We explored the relationship between hypoxia and vascular function in breast tumours through combined 18F-fluoromisonidazole (18 F-FMISO) PET/MRI, with simultaneous assessment circumventing the effect of temporal variation in hypoxia and perfusion.MethodsWomen with histologically confirmed, primary breast cancer underwent a simultaneous 18F-FMISO-PET/MR examination. Tumour hypoxia was assessed using influx rate constant Ki and hypoxic fractions (%HF), while parameters of vascular function (Ktrans, kep, ve, vp) and cellularity (ADC) were derived from dynamic contrast-enhanced (DCE) and diffusion-weighted (DW)-MRI, respectively. Additional correlates included histological subtype, grade and size. Relationships between imaging variables were assessed using Pearson correlation (r).ResultsTwenty-nine women with 32 lesions were assessed. Hypoxic fractions > 1% were observed in 6/32 (19%) cancers, while 18/32 (56%) tumours showed a %HF of zero. The presence of hypoxia in lesions was independent of histological subtype or grade. Mean tumour Ktrans correlated negatively with Ki (r = − 0.38, p = 0.04) and %HF (r = − 0.33, p = 0.04), though parametric maps exhibited intratumoural heterogeneity with hypoxic regions colocalising with both hypo- and hyperperfused areas. No correlation was observed between ADC and DCE-MRI or PET parameters. %HF correlated positively with lesion size (r = 0.63, p = 0.001).ConclusionHypoxia measured by 18F-FMISO-PET correlated negatively with Ktrans from DCE-MRI, supporting the hypothesis of perfusion-driven hypoxia in breast cancer. Intratumoural hypoxia-perfusion relationships were heterogeneous, suggesting that combined assessment may be needed for disease characterisation, which could be achieved using simultaneous multimodality imaging.Key Points• At the tumour level, hypoxia measured by 18F-FMISO-PET was negatively correlated with perfusion measured by DCE-MRI, which supports the hypothesis of perfusion-driven hypoxia in breast cancer.• No associations were observed between 18F-FMISO-PET parameters and tumour histology or grade, but tumour hypoxic fractions increased with lesion size.• Intratumoural hypoxia-perfusion relationships were heterogeneous, suggesting that the combined hypoxia-perfusion status of tumours may need to be considered for disease characterisation, which can be achieved via simultaneous multimodality imaging as reported here.

Main factors dominating the development, formation and dissipation of hypoxia off the Changjiang Estuary (CE) and its adjacent waters, China

Hypoxia off the Changjiang Estuary (CE) and its adjacent waters is purported to be the most severe in China, attracting considerable concern from both the scientific community and the general public. Currently, continuous observations of dissolved oxygen (DO) levels covering hypoxia from its appearance to disappearance are lacking. In this study, twelve consecutive monthly cruises (from February 2015 to January 2016) were conducted. The consecutive spatiotemporal variations in hypoxia throughout the annual cycle were elucidated in detail, and the responses of annual variations in hypoxia to the different influential factors were explored. Overall, hypoxia experienced a consecutive process of expanding from south to north, then disappearing from north to south. The annual variations in hypoxia were mainly contingent on stratification variations. Among different stages, there was significant heterogeneity in the dominant factors. Specifically, low-DO waters initially appeared from the intrusion of nearshore Kuroshio branch current (NKBC), as NKBC intrusion provided a low-DO background and triggered stratification. Thereafter, stratification was enhanced and gradually expanded northward, which promoted the extension of low-DO areas. The formation of hypoxia was regionally selective, and more intense organic matter decomposition at local regions facilitated the occurrence and discontinuous distribution of hypoxia. Hypoxic zones were observed at the Changjiang bank and Zhejiang coastal region from August (most extensively at 14,800 km2) to October. Thereafter, increased vertical mixing facilitated the dissipation of hypoxia from north to south.

Abstract 2443: Oxygen metabolism and hypoxia tolerance in organoid models of pancreatic ductal adenocarcinoma

Abstract Background: Pancreatic Ductal Adenocarcinoma (PDAC) has extremely heterogeneous hypoxic microenvironments across patients and high levels of hypoxia are correlated with increased tumor aggressiveness and resistance to therapy. However, the underlying genetic contributors to variations in hypoxia and its importance to the disease is currently unknown. We hypothesize that genetic mutations in PDAC associated with two principal factors - oxygen metabolism and hypoxia tolerance - influence the steady state levels of hypoxia in individual tumors. The demand for oxygen, which is influenced by genetic driven changes in cellular metabolism, define the levels and steepness of hypoxia gradients around perfused vessels. Tolerance to hypoxia determines the time tumor cells can survive in severe microenvironments depleted of oxygen and other nutrients. Both factors are affected by the activation of adaptive hypoxia stress response pathways including the HIF, UPR, and autophagy pathways. Method: We developed patient-derived-organoids from PDAC tumors for in vitro studies of oxygen metabolism and glycolytic rates using the Seahorse XF96. We also characterized hypoxia tolerance through monitoring of organoid growth and secondary growth under defined levels of oxygenation. In addition, we have developed an immunofluorescence image analysis pipeline to evaluate in vivo oxygen demand/consumption through the quantification of oxygen and proliferation gradients around perfused blood vessels. Results: We observed significant heterogeneities in oxygen metabolism and hypoxia tolerance across our patient derived organoid models. We also demonstrated the importance of PERK/UPR pathway in mediating both oxygen metabolism and hypoxia tolerance through regulation of ULK1, a kinase involved in the initiation of autophagy. Inhibition or knockdown of ULK1 decreased cell survival and correspondingly sensitized cells to hypoxia in organoid and tumor models. This is accompanied by accumulation of mitochondria and a corresponding increase in oxygen consumption, resulting in increased development of hypoxic cells. Conclusion: These experiments demonstrate the dual importance of oxygen metabolism and hypoxia tolerance and set the stage for the evaluation of these parameters and identification of the underlying genetic drivers of the hypoxic microenvironment. These genetic markers would be used for patient-selection and development of hypoxia-targeted therapies. Citation Format: Ji Zhang, Qingquan Liu, Dan Cojocari, Mark Zaidi, Trevor McKee, Nikolina Radulovich, Ming-Sound Tsao, David Hedley, Marianne Koritzinsky, Bradly G. Wouters. Oxygen metabolism and hypoxia tolerance in organoid models of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2443.

Intrusion of the Kuroshio Subsurface Water in the southern East China Sea and its variation in 2014 and 2015 traced by dissolved inorganic iodine species

The circulation systems and ecological environment of the East China Sea (ECS) are greatly influenced by the Kuroshio. The nutrient-rich Kuroshio Subsurface Water (KSSW) has been subject to considerable research attention, but the intrusion pathway, extent and variation of the KSSW over the entire southern ECS shelf are still debated. In June 2015, the dissolved inorganic iodine species (DIIS) were determined, and hydrographic data were collected and analyzed in the southern ECS. Analysis of the collected data suggests that the KSSW mainly intrudes onto the ECS shelf from northeast of Taiwan and bifurcates into a nearshore branch and an offshore branch. The nearshore branch ultimately appears in the subsurface layer within the 50-m isobath off the Zhejiang coast, north of 30 °N, and the offshore branch flows along the 100-m isobath and covers the area outside the 80-m isobath. Another KSSW intrusion along the shelf edge is located at ∼28 °N. This additional KSSW intrusion is weaker, and the offshore area in the southern ECS is mainly influenced by the KSSW intrusion northeast of Taiwan. Compared with the KSSW intrusion on the ECS continental shelf (depth < 100 m) in May 2014, the KSSW intrusion northeast of Taiwan in June 2015 was shifted seaward, had a greater geographical reach and intruded farther north off the Zhejiang coast. The KSSW intrusion in the nearshore area off the Zhejiang coast may promote a decrease in dissolved oxygen (DO) in the bottom water as well as the growth of phytoplankton in the upper water. The expansion of the range of the KSSW intrusion northward in 2015 led to the movement of the low-DO, high-chlorophyll area farther north in 2015 relative to its position in 2014 and may have contributed to the variations in hypoxia and algal blooms.

Variations in Hypoxia Impairs Muscle Oxygenation and Performance during Simulated Team-Sport Running.

Purpose: To quantify the effect of acute hypoxia on muscle oxygenation and power during simulated team-sport running.Methods: Seven individuals performed repeated and single sprint efforts, embedded in a simulated team-sport running protocol, on a non-motorized treadmill in normoxia (sea-level), and acute normobaric hypoxia (simulated altitudes of 2,000 and 3,000 m). Mean and peak power was quantified during all sprints and repeated sprints. Mean total work, heart rate, blood oxygen saturation, and quadriceps muscle deoxyhaemoglobin concentration (assessed via near-infrared spectroscopy) were measured over the entire protocol. A linear mixed model was used to estimate performance and physiological effects across each half of the protocol. Changes were expressed in standardized units for assessment of magnitude. Uncertainty in the changes was expressed as a 90% confidence interval and interpreted via non-clinical magnitude-based inference.Results: Mean total work was reduced at 2,000 m (−10%, 90% confidence limits ±6%) and 3,000 m (−15%, ±5%) compared with sea-level. Mean heart rate was reduced at 3,000 m compared with 2,000 m (−3, ±3 min−1) and sea-level (−3, ±3 min−1). Blood oxygen saturation was lower at 2,000 m (−8, ±3%) and 3,000 m (−15, ±2%) compared with sea-level. Sprint mean power across the entire protocol was reduced at 3,000 m compared with 2,000 m (−12%, ±3%) and sea-level (−14%, ±4%). In the second half of the protocol, sprint mean power was reduced at 3,000 m compared to 2,000 m (−6%, ±4%). Sprint mean peak power across the entire protocol was lowered at 2,000 m (−10%, ±6%) and 3,000 m (−16%, ±6%) compared with sea-level. During repeated sprints, mean peak power was lower at 2,000 m (−8%, ±7%) and 3,000 m (−8%, ±7%) compared with sea-level. In the second half of the protocol, repeated sprint mean power was reduced at 3,000 m compared to 2,000 m (−7%, ±5%) and sea-level (−9%, ±5%). Quadriceps muscle deoxyhaemoglobin concentration was lowered at 3,000 m compared to 2,000 m (−10, ±12%) and sea-level (−11, ±12%).Conclusions: Simulated team-sport running is impaired at 3,000 m compared to 2,000 m and sea-level, likely due to a higher muscle deoxygenation.

Relationships Between Long-Term Trend of Satellite-Derived Chlorophyll-a and Hypoxia Off the Changjiang Estuary

The Changjiang Estuary is one of the largest estuaries in the world, where hypoxia frequently occurs during the summer season. Recent routine surveys in the observed area found that the low dissolved oxygen (DO) in the summer bottom water was not rapidly expanding with increasing nutrient loads in Changjiang diluted waters. Based on the remote sensing data and in situ data, we examined the historic seasonal hypoxia observations for the bottom waters of the Changjiang Estuary and investigated the short- and long-term effects that runoff had on variations in DO and chlorophyll-a (Chl-a). Our analysis indicated that the recent areal variation in hypoxia was due to the changing Chl-a distribution and stratification conditions. The correspondence between hypoxia and surface Chl-a concentration showed that remotely sensed Chl-a larger than 3.0 mg L−1 was an essential condition for the formation of hypoxia off the Changjiang Estuary. The trend of Chl-a concentration was significantly impacted by the Three Gorges Dam (TGD), and the inter-annual variation of Chl-a was weakly affected by global-scale climate variability. After the TGD impoundment, the sediment loading in the Changjiang runoff and suspended sediments in Changjiang Estuary in August decreased, and the high Chl-a concentration moved landward. These shifted the hypoxia from its optimal forming conditions.

The contribution of physical processes to inter‐annual variations of hypoxia in Chesapeake Bay: A 30‐yr modeling study

A numerical circulation model with a very simple representation of dissolved oxygen dynamics is used to simulate hypoxia in Chesapeake Bay for the 30-yr period 1984–2013. The model assumes that the biological utilization of dissolved oxygen is constant in both time and space in an attempt to isolate the role that physical processes play in modulating oxygen dynamics. Despite the simplicity of the model it demonstrates skill in simulating the observed inter-annual variability of hypoxic volume, capturing 50% of the observed variability in hypoxic volume (<2 mg L−1) for the month of July and 58% of the observed variability for the month of August, over the 30-yr period. Model skill increases throughout the summer suggesting that physical processes play a more important role in modulating hypoxia later in the summer. Model skill is better for hypoxic volumes than for anoxic volumes. In fact, a simple regression based on the integrated January–June Susquehanna River nitrogen load can explain more of the variability in the observed anoxic volumes than the model presented here. Model results suggest that the mean summer (June–August) wind speed is the single-most important physical variable contributing to variations in hypoxic volumes. Previous studies have failed to document the importance of summer wind speed because they have relied on winds measured at Patuxent Naval Air Station, which does not capture the observed inter-annual variations in wind speed that are observed by stations that directly measure wind over the waters of Chesapeake Bay.

Androgen withdrawal fails to induce detectable tissue hypoxia in the rat prostate

It has been reported that significant hypoxia may occur in the rat prostate following androgen deprivation (AD). It is well known that hypoxia substantially reduces radiation sensitivity of cells both in vitro and in vivo. Given that contemporary management of men with intermediate and high-risk prostate cancer includes the use of neoadjuvant androgen suppression and radiation, AD-induced hypoxia in the prostate could result in suboptimal therapeutic results. Given this concern, we fully investigate possible AD-induced hypoxia in the ventral prostate (VP) of adult rats by two independent methods. Tissue pO2 levels in the VP of adult Spraque-Dawley rats were evaluated prior to and at various time points following castration by two independent techniques. First, an Oxylab tissue oxygen monitor with a 240 μm probe was used for quantitative monitoring of global VP oxygenation. Second, fluorescence immunohistochemistry using the hypoxia marker EF5, known to be metabolically activated by hypoxic cells, was used to evaluate cell-to-cell variation in hypoxia at various days post-castration. Neither the oxygen probe nor EF5 method demonstrate any substantive change in pO2 levels in the rat VP at any time point post-castration. We find no evidence that the rat VP becomes hypoxic at any point following castration using an animal model that closely mimics the human prostate. These data are in contrast to previous reports suggesting prostatic hypoxia occurs following AD and provide assurance that our present therapeutic strategy of neoadjuvant AD followed by radiation is not compromised by AD-induced tissue hypoxia.

Linking dynamics of transport timescale and variations of hypoxia in the Chesapeake Bay

[1] Dissolved oxygen (DO) replenishment in the bottom waters of an estuary depends on physical processes that are significantly influenced by external forcings. The vertical exchange time (VET) is introduced in this study to quantify the physical processes that regulate the DO replenishment in the Chesapeake Bay. A 3-D numerical model was applied to simulate the circulation, VET, and DO. Results indicate that VET is a suitable parameter for evaluating the bottom DO condition over both seasonal and interannual timescales. The VET is negatively correlated with the bottom DO. Hypoxia (DO 23 days) can account for 77% of variations of hypoxic volume in the main Bay. The VET cannot explain all the DO variations as it can only account for the contribution of physical processes that regulate DO replenishment. It is found that the short-term vertical exchange process is highly controlled by the wind forcing. The VET volume decreases when the high-speed wind events are frequent. The summertime VET volume is less sensitive to short-term variations (pulses) of river discharge. It is sensitive to the total amount of river discharge and the high VET volume can be expected in the wet year.

Parameterisation of oxygen dynamics in the bottom water of the Baltic Sea-North Sea transition zone

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 481:25-39 (2013) - DOI: https://doi.org/10.3354/meps10220 Parameterisation of oxygen dynamics in the bottom water of the Baltic Sea-North Sea transition zone Jørgen L. S. Hansen1,*, Jørgen Bendtsen2 1Department of Bioscience, University of Aarhus, Frederiksborgvej 399, 4000 Roskilde, Denmark 2ClimateLab, Symbion Science Park, Fruebjergvej 3, boks 98, 2100 Copenhagen Ø, Denmark *Email: joh@dmu.dk ABSTRACT: An organic carbon budget for the Kattegat and Belt Seas in the North Sea-Baltic Sea transition zone was used to parameterise the pelagic and benthic respiration in a new oxygen model, OXYCON, which describes the influence of temperature-dependent pelagic and benthic respiration on bottom water oxygen conditions. The significance of respiration versus physical mixing and advection processes for the bottom water oxygen concentration was analysed through a sensitivity study where the OXYCON model was implemented in 2 transport models: a Lagrangian model of bottom water transport, based on an age-tracer of the bottom water transit-time through the area, and a 3-dimensional circulation model of the transition zone. The solutions of both models were in accordance with the observed spatial and temporal distribution of oxygen in the area during the period 2001 to 2003. In particular, the temporal and spatial dynamics of a severe hypoxic event in 2002 were well described. The inter-annual variability of hypoxia during this period could therefore be explained by changes in physical mixing and ventilation of the bottom layer with oxygen-rich surface water and by the bottom water temperature. Variability in the sources of organic material available for remineralisation in the bottom water seems to have less influence on the inter-annual variation in hypoxia but instead determines the background conditions and the long-term trend in oxygen dynamics. KEY WORDS: Hypoxia · Carbon mineralisation · Respiration · Baltic Sea · Kattegat · Modelling Full text in pdf format PreviousNextCite this article as: Hansen JLS, Bendtsen J (2013) Parameterisation of oxygen dynamics in the bottom water of the Baltic Sea-North Sea transition zone. Mar Ecol Prog Ser 481:25-39. https://doi.org/10.3354/meps10220 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 481. Online publication date: May 07, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Spatial relationship of phosphorylated epidermal growth factor receptor and activated AKT in head and neck squamous cell carcinoma

BackgroundOverexpression of EGFR correlates with decreased survival after radiotherapy in head and neck squamous cell carcinoma (HNSCC). However, the contribution of the activated form, pEGFR, and its downstream signaling (PI3-K/AKT) pathway is not clear yet. MethodsFifty-eight patients with HNSCC were included in the study. pEGFR, pAKT, hypoxia, and vessels were visualized using immunohistochemistry. Fractions (defined as the tumor area positive for the respective markers relative to the total tumor area) were calculated by automated image analysis and related to clinical outcome. ResultsBoth pEGFR (median 0.6%, range 0–34%) and pAKT (median 1.8%, range 0–16%) expression differed between tumors. Also, a large variation in hypoxia was found (median pimonidazole fraction 3.9% 0–20%). A significant correlation between pEGFR and pAKT (rs 0.44, p=0.004) was seen, however, analysis revealed that this was not always based on spatial coexpression. Low pAKT expression was associated with increased risk of regional recurrence (p<0.05, log-rank) and distant metastasis (p=0.04). ConclusionThe correlation between expression of pEGFR and pAKT is indicative of activation of the PI3-K/AKT pathway through phosphorylation of EGFR. Since not all tumors show coexpression to the same extent, other factors must be involved in the activation of this pathway as well.

A simple 1-dimensional, climate based dissolved oxygen model for the central basin of Lake Erie

A linked 1-dimensional thermal-dissolved oxygen model was developed and applied in the central basin of Lake Erie. The model was used to quantify the relative contribution of meteorological forcings versus the decomposition of hypolimnetic organic carbon on dissolved oxygen. The model computes daily vertical profiles of temperature, mixing, and dissolved oxygen for the period 1987–2005. Model calibration resulted in good agreement with observations of the thermal structure and oxygen concentrations throughout the period of study. The only calibration parameter, water column oxygen demand (WCOD), varied significantly across years. No significant relationships were found between these rates and the thermal properties; however, there was a significant correlation with soluble reactive phosphorus loading. These results indicate that climate variability alone, expressed as changes in thermal structure, does not account for the inter-annual variation in hypoxia. Rather, variation in the production of organic matter is a dominant driver, and this appears to have been responsive to changes in phosphorus loads.

‘Desperate house genes’: the dramatic example of hypoxia

Background:Microenvironmental conditions in normal or tumour tissues and cell lines may interfere on further biological analysis. To evaluate transcript variations carefully, it is common to use stable housekeeping genes (HKG) to normalise quantitative microarrays or real-time polymerase chain reaction results. However, recent studies argue that HKG fluctuate according to tissues and treatments. So, as an example of HKG variation under an array of conditions that are common in the cancer field, we evaluate whether hypoxia could have an impact on HKG expression.Methods:Expression of 10 commonly used HKG was measured on four cell lines treated with four oxygen concentrations (from 1 to 20%).Results:Large variations of HKG transcripts were observed in hypoxic conditions and differ along with the cell line and the oxygen concentration. To elect the most stable HKG, we compared the three statistical means based either on PCR cycle threshold coefficient of variation calculation or two specifically dedicated software. Nevertheless, the best HKG dramatically differs according to the statistical method used. Moreover, using, as a reference, absolute quantification of a target gene (here the proteinase activating receptor gene 1 (PAR1) gene), we show that the conclusions raised about PAR1 variation in hypoxia can totally diverge according to the selected HKG used for normalisation.Conclusion:The choice of a valid HKG will determine the relevance of the results that will be further interpreted, and so it should be seriously considered. The results of our study confirm unambiguously that HKG variations must be precisely and systematically determined before any experiment for each situation, to obtain reliable normalised results in the experimental setting that has been designed. Indeed, such assay design, functional for all in vitro systems, should be carefully evaluated before any extension to other experimental models including in vivo ones.

Generation Mechanism and Movement of Hypoxia in Strongly Enclosed Waters of Ports and Harbors

We conducted field observations in relation to hypoxia which occurs in strongly enclosed waters, such as ports and harbors, and examined generation mechanism and movement of hypoxia. Diurnal variations in hypoxia were driven by tide and wind in the strongly enclosed waters in the head of Osaka Bay. It was found that processes of the organism decomposition, oxygen consumption and carbon dioxide generation were different in and out of the ports. In the spring and summer when the water column is stratified, surface water absorbs CO2 and bottom water stores CO2 in strongly enclosed waters. On the other hand, in the end of summer, the stored CO2 upwells to the surface and causes spontaneous emission because the north wind induces the upwelling.

Predicting the effect of temporal variations in p o2 on tumor radiosensitivity

Purpose Tumor hypoxia is associated with less effective radiation-mediated cell killing, increased metastatic potential, and poorer prognosis. Transient variations in hypoxia, with characteristic periodicity on the order of 1 to 10 min, have been observed in animal models. This article explores the effect of these temporal variations in P o 2 on the oxygen enhancement ratio, effective radiation dose to the tumor, and tumor control probability. Methods and materials P o 2 over a 50–60 min period was determined at multiple sites in rat fibrosarcomas, 9L gliomas, and R3230Ac mammary adenocarcinomas. Using a correlation derived from the data of Elkind et al. (1965), P o 2 data are converted into oxygen enhancement ratios (OERs.) A tumor is assumed to consist of 10 3–10 4 independent oxygenation subvolumes, each with a randomly chosen starting point on the OER-time curve. The effect of temporal variations in OER is examined for three cases: conventionally fractionated external beam radiotherapy (EBRT), stereotactic radiosurgery (SRS) and intraoperative radiotherapy (IORT). The oxygen effective dose (OED) for a subvolume is calculated from the dose to that subvolume modified by the OER. In turn, the distribution of OED for a tumor is analyzed for each treatment case and representative tumor control probabilities (TCPs) calculated. Results Oxygen enhancement ratio varied from 1 to 3 over the range of P o 2 measured in this study. Mean OER ranged from 1.6 to 2.6, and the variation in OER vs. time was greater with decreasing P o 2. In EBRT, the standard deviation in OED was small, <2%. In contrast, the standard deviation in OED was much higher for both SRS and IORT, typically ranging from 3 to 6%, with the greatest variation at the lowest P o 2s. Compared with a tumor with equal mean OED and uniform P o 2, TCP was minimally poorer for either EBRT or well-oxygenated tumors. However, for both SRS and IORT, temporal variations in more hypoxic tumors can produce a significant decrease in TCP. Conclusion Temporal variations in tumor P o 2 can produce significant variations OER, particularly at low P o 2, resulting in decreased TCP for hypofractionated treatment regimens.

Cardiovascular Effects of 8 h of Isocapnic Hypoxia with and without Beta-Blockade in Humans

This study seeks to confirm the progressive changes in cardiac output and heart rate previously reported with 8 h exposures to constant hypoxia, and to examine the role of sympathetic mechanisms in generating these changes. Responses of ten subjects to four 8 h protocols were compared: (1) air breathing with placebo; (2) isocapnic hypoxia (end-tidal PO2 = 50 mm Hg) with placebo; (3) isocapnic hypoxia with beta-blockade; and (4) air breathing with beta -blockade. Regular measurements of heart rate and cardiac output (using ultrasonography and N2O rebreathing techniques) were made with subjects seated in the upright position. The sensitivity of heart rate to rapid variations in hypoxia (GHR) and heart rate in the absence of hypoxia were measured at times 0, 4 and 8 h. No significant progressive effect of hypoxia on cardiac output was detected. There was a gradual rise in heart rate with hypoxia of 11+/-2 beats min(-1) in the placebo protocol and of 10+/-2 beats min(-1) in the beta-blockade protocol over 8 h, compared to the air breathing protocols. The rise in heart rate was progressive (P<0.001) and accompanied by progressive increases in both GHR (P<0.001) and heart rate measured in the absence of hypoxia (P<0.05). No significant effect of beta-blockade was detected on any of these progressive changes. We conclude that sympathetic mechanisms that act via beta -receptors play little role in the progressive changes in heart rate observed over 8 h of moderate hypoxia.

The effect of carotid sinus denervation on fetal heart rate variation in normoxia, hypoxia and post-hypoxia in fetal sheep.

To investigate whether carotid sinus nerve reflexes are linked to the increase in heart rate variation in acute (one hour) hypoxia in late gestation fetal sheep Comparison of short term variation between intact and carotid sinus denervated fetuses in normoxia, hypoxia and post-hypoxia. Sixteen chronically catheterised pregnant sheep in late gestation. There was no significant difference in short term variation between intact and denervated fetuses in normoxia. In intact fetuses short term variation increased significantly in hypoxia. In denervated fetuses it tended to increase in hypoxia, but this was not statistically significant. During the post-hypoxia period, short term variation increased significantly in denervated fetuses, although at this time it was decreasing in intact fetuses. When the decrease in pH was small intact fetuses showed a significantly greater increase in short term variation than denervated fetuses in hypoxia. In contrast, short term variation increased similarly in both groups when the pH decrease was greater (> 0.03 in early hypoxia and > 0.05 in late hypoxia). Carotid sinus nerve reflexes have an important influence on heart rate variation in hypoxia and post-hypoxia. It appears that other mechanisms (e.g. a rise in circulating catecholamines) are linked to an increase in heart rate variation when mild acidemia occurs in hypoxia.