•Dose calculations between synthetic CT and planning CT acquired at the same treatment fraction have small differences.•The safe omission of repeat CT during H&N RT is feasible when CBCT is ...available.•Synthetic CT verification appears to overestimate the need to re-plan, therefore not putting patients at risk.•Repeat CT should be used for replanning, being guided by CBCT and synthetic CT.
The study aimed to assess the suitability of deformable image registration (DIR) software to generate synthetic CT (sCT) scans for dose verification during radiotherapy to the head and neck. Planning and synthetic CT dose volume histograms were compared to evaluate dosimetric changes during the treatment course.
Eligible patients had locally advanced (stage III, IVa and IVb) oropharyngeal cancer treated with primary radiotherapy. Weekly CBCT images were acquired post treatment at fractions 1, 6, 11, 16, 21 and 26 over a 30 fraction treatment course. Each CBCT was deformed with the planning CT to generate a sCT which was used to calculate the dose at that point in the treatment. A repeat planning CT2 was acquired at fraction 16 and deformed with the fraction 16 CBCT to compare differences between the calculations mid-treatment.
20 patients were evaluated generating 138 synthetic CT sets. The single fraction mean dose to PTV_HR between the synthetic and planning CT did not vary, although dose to 95% of PTV_HR was smaller at week 6 compared to planning (difference 2.0%, 95% CI (0.8 to 3.1), p = 0.0). There was no statistically significant difference in PRV_brainstem or PRV_spinal cord maximum dose, although greater variation using the sCT calculations was reported. The mean dose to structures based on the fraction 16 sCT and CT2 scans were similar.
Synthetic CT provides comparable dose calculations to those of a repeat planning CT; however the limitations of DIR must be understood before it is applied within the clinical setting.
The oligometastatic paradigm suggests that some patients with a limited number of metastases might be cured if all lesions are eradicated. Evidence from randomised controlled trials to support this ...paradigm is scarce. We aimed to assess the effect of stereotactic ablative radiotherapy (SABR) on survival, oncological outcomes, toxicity, and quality of life in patients with a controlled primary tumour and one to five oligometastatic lesions.
This randomised, open-label phase 2 study was done at 10 hospitals in Canada, the Netherlands, Scotland, and Australia. Patients aged 18 or older with a controlled primary tumour and one to five metastatic lesions, Eastern Cooperative Oncology Group score of 0–1, and a life expectancy of at least 6 months were eligible. After stratifying by the number of metastases (1–3 vs 4–5), we randomly assigned patients (1:2) to receive either palliative standard of care treatments alone (control group), or standard of care plus SABR to all metastatic lesions (SABR group), using a computer-generated randomisation list with permuted blocks of nine. Neither patients nor physicians were masked to treatment allocation. The primary endpoint was overall survival. We used a randomised phase 2 screening design with a two-sided α of 0·20 (wherein p<0·20 designates a positive trial). All analyses were intention to treat. This study is registered with ClinicalTrials.gov, number NCT01446744.
99 patients were randomised between Feb 10, 2012, and Aug 30, 2016. Of 99 patients, 33 (33%) were assigned to the control group and 66 (67%) to the SABR group. Two (3%) patients in the SABR group did not receive allocated treatment and withdrew from the trial; two (6%) patients in the control group also withdrew from the trial. Median follow-up was 25 months (IQR 19–54) in the control group versus 26 months (23–37) in the SABR group. Median overall survival was 28 months (95% CI 19–33) in the control group versus 41 months (26–not reached) in the SABR group (hazard ratio 0·57, 95% CI 0·30–1·10; p=0·090). Adverse events of grade 2 or worse occurred in three (9%) of 33 controls and 19 (29%) of 66 patients in the SABR group (p=0·026), an absolute increase of 20% (95% CI 5–34). Treatment-related deaths occurred in three (4·5%) of 66 patients after SABR, compared with none in the control group.
SABR was associated with an improvement in overall survival, meeting the primary endpoint of this trial, but three (4·5%) of 66 patients in the SABR group had treatment-related death. Phase 3 trials are needed to conclusively show an overall survival benefit, and to determine the maximum number of metastatic lesions wherein SABR provides a benefit.
Ontario Institute for Cancer Research and London Regional Cancer Program Catalyst Grant.
Hydrogen sulphide (H2S) is toxic and can act as a selective pressure on aquatic organisms, facilitating a wide range of adaptations for life in sulphidic environments. Mangrove rivulus (Kryptolebias ...marmoratus) inhabit mangrove swamps and have developed high tolerance to environmental H2S. They are hermaphroditic and can self-fertilize, producing distinct isogenic lineages with different sensitivity to H2S. Here, we tested the hypothesis that observed differences in responses to H2S are the result of differences in mitochondrial functions. For this purpose, we performed two experimental series, testing (1) the overall mitochondrial oxidizing capacities and (2) the kinetics of apparent H2S mitochondrial oxidation and inhibition in two distinct lineages of mangrove rivulus, originally collected from Belize and Honduras. We used permeabilized livers from both lineages, measured mitochondrial oxidation, and monitored changes during gradual increases of sulphide. Ultimately, we determined that each lineage has a distinct strategy for coping with elevated H2S, indicating divergences in mitochondrial function and metabolism. The Honduras lineage has higher anaerobic capacity substantiated by higher lactate dehydrogenase activity and higher apparent H2S oxidation rates, likely enabling them to tolerate H2S by escaping aquatic H2S in a terrestrial environment. However, Belize fish have increased cytochrome c oxidase and citrate synthase activities as well as increased succinate contribution to mitochondrial respiration, allowing them to tolerate higher levels of aquatic H2S without inhibition of mitochondrial oxygen consumption. Our study reveals distinct physiological strategies in genetic lineages of a single species, indicating possible genetic and/or functional adaptations to sulphidic environments at the mitochondrial level.
Natural temperature variation in many marine ecosystems is stochastic and unpredictable and climate change models indicate that this thermal irregularity is likely to increase. Temperature ...acclimation may be more challenging when conditions are highly variable and stochastic and there is a need for empirical physiological data in these thermal environments. Using the hermaphroditic, amphibious Mangrove rivulus (Kryptolebias marmoratus) we hypothesized that compared to regular, warming diel thermal fluctuations, stochastic warm fluctuations would negatively affect physiological performance. To test this, we acclimated fish to: 1) non-stochastic and 2) stochastic thermal fluctuations (27°C -35°C) with a similar thermal load, and 3) a stable/consistent control temperature at the low end of the cycle (27°C). We determined that fecundity was reduced in both cycles, with reproduction ceasing in stochastic thermal environments. Fish acclimated to non-stochastic thermal cycles had growth rates lower than those of control fish. Exposure to warm, fluctuating cycles did not affect emersion temperature and only regular diel cycles modestly increased critical thermal tolerance (CTmax). We predicted that warm diel cycling temperatures would increase gill surface area. Notably, fish acclimated to either thermal cycle had a reduced gill surface area and increased intralamellar cell mass (ILCM) when compared to control fish. This decreased gill surface area with warming contrasts with what is observed for exclusively aquatic fish and suggests a preparatory gill response for emersion in these amphibious fish. Collectively, our data reveal the importance of considering stochastic thermal variability when studying the effects of temperature on fishes.
Understanding factors affecting ectothermic fishes' capacity to cope with warming temperature is critical given predicted climate change scenarios. We know that a fish's social environment introduces ...plasticity in how it responds to high temperature. However, the magnitude of this plasticity and the mechanisms underlying socially-modulated thermal responses are unknown. Using the amphibious, selfing hermaphroditic mangrove rivulus fish (Kryptolebias marmoratus) as a model, we tested three hypotheses: 1) social stimulation affects physiological and behavioural thermal responses of isogenic lineages of fish, 2) social experience and acute social stimulation result in distinct physiological and behavioural responses, and 3) a desensitization of thermal receptors is responsible for socially modulated thermal responses. To test the first two hypotheses, we measured the temperature at which fish emerged (i.e., pejus temperature) with acute warming with socially naïve, isolated fish and with fish that were raised alone and then given a short social experience prior to exposure to increasing temperature (i.e., socially experienced fish). Our results did not support our first hypothesis as fish socially-stimulated by mirrors during warming (i.e., acute social stimulation) emerged at similar temperatures as isolated fish. However, in support of our second hypothesis, a short period of prior social experience resulted in fish emerging at a higher temperature than socially naïve fish suggesting an increase in pejus temperature with social experience. To test our third hypothesis, we exposed fish having had a brief social interaction and naïve fish to capsaicin, an agonist of TRPV1 thermal receptors. Socially experienced fish emerged at significantly higher capsaicin concentrations than socially naïve fish suggesting a desensitization of their TRPV1 thermal receptors. Collectively, our data indicate that past and present social experiences impact the behavioural response of fish to high temperature. We also provide novel data suggesting that brief periods of social experience affects the capacity of fish to perceive warm temperature.
Freshwater fish face a variety of spatiotemporal thermal challenges throughout their life. On a broad scale, temperature is an important driver of physiological, behavioural and ecological patterns ...and ultimately affects populations and overall distribution. These broad patterns are partly underpinned by the small‐scale local effects of temperature on individuals within the population. Climate change is increasing the range of daily thermal variation in most freshwater ecosystems, altering behaviour and performance of resident fishes. The aim of this review is understanding how daily thermal variation in temperate rivers affects individual fish physiology, behaviour and overall performance. The following are highlighted in this study: (a) the physical characteristics of rivers that can either buffer or exacerbate thermal variability, (b) the effects of thermal variability on growth and metabolism, (c) the approaches for quantifying thermal variation and thermal stress and (d) how fish may acclimatize or adapt to our changing climate.
We designed two environmentally relevant thermal cycling regimes using monitoring data from an Atlantic salmon (Salmo salar) river to determine whether exposure to prior diel cycles stimulated ...protective mechanisms (e.g., heat hardening) and (or) resulted in physiological and cellular stress. Wild fish were exposed to 3 days of diel cycling in the lab and then exposed to an acute thermal challenge near their upper reported critical temperature. We measured routine metabolic rate across the time course as well as indicators of physiological status (e.g., plasma glucose and osmolality) and cellular stress (e.g., heat shock protein 70). We observed that thermal cycling altered physiological and cellular responses, compared with an acute heat shock, but saw no differences between cycling regimes. Unique temperature regime and tissue-specific responses were observed in heat shock protein induction, metabolites, haematology, and osmotic indicators. Routine metabolic rate was not affected by the thermal cycling and increased according to Q
10
predictions. While we report unique physiological and cellular responses among all treatment groups, we did not observe a clear indication of a heat hardening response.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Mangroves are critical marine habitats. High hydrogen sulphide
(
H
2
S) is a feature of these important ecosystems and its toxicity creates a challenge for mangrove inhabitants. The mangrove rivulus ...(
Kryptolebias marmoratus
) is a selfing, hermaphroditic, amphibious fish that can survive exposure to 1116 μM H
2
S in the wild. These fish rely on cutaneous respiration for gas and ion exchange when emerged. We hypothesized that the skin surface is fundamentally important in H
2
S tolerance in these mangrove fish by limiting H
2
S permeability. To test our hypothesis, we first disrupted the skin surface in one isogenic lineage and measured H
2
S tolerance and sensitivity. We increased water H
2
S concentration until emersion as a measure of the ability to sense and react to H
2
S, which we refer to as sensitivity. We then determined H
2
S tolerance by preventing emersion and increasing H
2
S until loss of equilibrium (LOE). The H
2
S concentration at emersion and LOE were significantly affected by disrupting the skin surface, providing support that the skin is involved in limiting H
2
S permeability. Capitalizing on their unique reproductive strategy, we used three distinct isogenic lineages to test the hypothesis that there would be genetic differences in H
2
S sensitivity and tolerance. We found significant differences in emersion concentration only among lineages, suggesting a genetic component to H
2
S sensitivity but not tolerance. Our study also demonstrated that external skin modifications and avoidance behaviours are two distinct strategies used to tolerate ecologically relevant H
2
S concentrations and likely facilitate survival in challenging mangrove habitats.
Unlike enucleated mammalian red blood cells (rbcs), the nucleated rbcs of lower vertebrates are capable of protein synthesis and may, therefore, serve as a valuable model to investigate the adaptive ...significance of stress protein synthesis in cells. This study examined the synthesis of stress protein 70 (Hsp70) in rbcs of the temperature-sensitive rainbow trout Oncorhynchus mykiss in response to heat shock and anoxia. Through western blot analysis, we have demonstrated that rainbow trout rbcs synthesize Hsp70 both constitutively and in response to an increase in temperature. Radioisotopic labelling experiments indicated that the temperature at which Hsp70 synthesis was induced in fish acclimated to 10 °C was between 20 and 25 °C. Actinomycin D blocked de novo Hsp70 synthesis, implying that synthesis of Hsp70 is regulated at the level of transcription in rainbow trout rbcs. Since trout rbcs rely heavily on aerobic metabolism, but may also experience very low oxygen levels within the circulation, we also examined the relative importance of (1) anoxia as a stimulus for Hsp70 synthesis and (2) oxygen as a requirement for protein synthesis under control and heat-shock conditions. We found that trout rbcs were capable of protein synthesis during 2 h of anoxia, but did not increase Hsp70 synthesis. Moreover, rbcs subjected to combined anoxia and heat shock exhibited increases in Hsp70 synthesis that were similar in magnitude to those in cells exposed to heat shock alone. The latter results suggest that rainbow trout rbcs are (1) able to synthesize non-stress proteins during anoxia, (2) capable of tolerating periods of reduced oxygen availability without increased synthesis of stress proteins and (3) able to maintain the integrity of their heat-shock response even during periods of anoxia.
Social context can impact how animals respond to changes in their physical environment. We used an aggressive, amphibious fish, the mangrove rivulus (Kryptolebias marmoratus) with environmentally ...determined sociality to test the hypothesis that social interactions would push fish to their thermal limits. We capitalized on the propensity of rivulus to emerge from warming water and demonstrated that social stimuli, produced by their reflection, increased emersion threshold without changing the critical thermal maximum, effectively diminishing thermal safety margins. When rivulus were denied air access, surface behaviours dramatically increased, supplanting social interactions. This suggests that assessing the terrestrial environment is crucially important. We conclude that social stimulation narrows the scope for survival in naturally stressful conditions.
PDF
