Elevated Consumption Rates Research Articles

Oxygen consumption measurements at ultra-high dose rate over a wide LET range.

The role of radiolytic oxygen consumption for the in-vitro "Ultra-High Dose Rate" (UHDR) sparing and in-vivo FLASH effect is subject to active debate, but data on key dependencies such as the radiation quality are lacking. The influence of "dose-averaged Linear Energy Transfer" (LETd) and dose rate on radiolytic oxygen consumption was investigated by monitoring the oxygen concentration during irradiation with electrons, protons, helium, carbon, and oxygen ions at UHDR and "Standard Dose Rates" (SDR). Sealed "Bovine Serum Albumin" (BSA) 5% samples were exposed to 15Gy of electrons and protons, and for the first time helium, carbon, and oxygen ions with LETd values of 1, 5.4, 14.4, 65, and 100.3keV/µm, respectively, delivered at mean dose rates of either 0.3-0.4Gy/s for SDR or approximately 100Gy/s for UHDR. The Oxylite (Oxford Optronics) system allowed measurements of the oxygen concentration before and after irradiation to calculate the oxygen consumption rate. The oxygen consumption rate was found to decrease with increasing LETd from 0.351mmHg/Gy for low LET electrons to 0.1796mmHg/Gy for high LET oxygen ions at SDR and for UHDR from 0.317 to 0.1556mmHg/Gy, respectively. A higher consumption rate for SDR irradiation compared to the corresponding UHDR irradiation persisted for all particle types. The measured consumption rates demonstrate a distinct LETd dependence. The obtained dataset, encompassing a wide range of LETd values, could serve as a benchmark for Monte Carlo simulations, which may aid in enhancing our comprehension of oxygen-related mechanisms after irradiations. Ultimately, they could help assess the viability of different hypotheses regarding UHDR sparing mechanisms and the FLASH effect. The found LETd dependence underscores the potential of heavy ion therapy, wherein elevated consumption rates in adjacent normal tissue offer protective benefits, while leaving tumor regions with generally higher "Linear Energy Transfer" (LET) vulnerable.

Opioid Consumption Rate Following Foot and Ankle Surgery.

The rapid increase in the consumption of prescription opioids has become one of the leading medical, economic, and sociological burdens in North America. In the United States, orthopedic surgery is the fourth leading specialty in the number of opioids prescribed, and the largest among all operative specialties. There is insufficient evidence to guide surgeons about appropriate opioid prescription amounts after orthopedic foot and ankle (F&A) procedures. The aim of this study was to determine the opioid consumption rate after foot and ankle procedures and identify risk factors associated with higher use. A total of 535 patients who underwent foot and/or ankle surgery between August 2016 and March 2018 were included in the study. Each patient received a preoperative discussion about postoperative pain and expectations alongside a standardized handout. At the 2-week postoperative visit, the patients self-reported the amount of consumed opioids. Prescription details, number of opioid pills consumed, refill requests, pain-issue-related telephone calls, and additional physician/emergency department visits were documented. Patient demographics, comorbidities, use of regional anesthesia, hospitalization, surgery type/severity, and preoperative opioid use were collected. A total of 244 patients had a sufficiently complete data set for inclusion in the final cohort. Subjects had a mean age of 50 years (±16.3) and a body mass index (BMI) of 29 (±6.1). Sixty-six (27%) patients underwent a soft tissue procedure alone and 178 (73%) underwent a bony procedure. On average, patients consumed 46.6% of the prescribed pills following a bony procedure and 42.4% after a soft tissue procedure, which resulted in a total of 4496 leftover pills. BMI, procedure type (bony vs soft tissue)/severity, and number of opioids prescribed were positively correlated with elevated consumption rates (P = .008, P < .001, P < .001, P < .001, respectively). BMI, procedure type, and higher initial pill dispensation correlated with a larger number of consumed pills during the postoperative period. On average, patients took 42.4% of the prescribed opioid after soft tissue procedures and 46.6% after bony procedures, resulting in a significant number of unused pills. Future guidelines are necessary to improve postoperative pain management to prevent narcotic overprescription and minimize the downstream potential for unprescribed community opioid access. Level III, retrospective case series, analytic.

Quantity and quality limit detritivore growth: mechanisms revealed by ecological stoichiometry and co-limitation theory.

Resource quantity and quality are fundamental bottom-up constraints on consumers. Best understood in autotroph-based systems, co-occurrence of these constraints may be common but remains poorly studied in detrital-based systems. Here, we used a laboratory growth experiment to test limitation of the detritivorous caddisfly larvae Pycnopsyche lepida across a concurrent gradient of oak litter quantity (food supply) and quality (phosphorus : carbon [P:C ratios]). Growth increased simultaneously with quantity and quality, indicating co-limitation across the resource gradients. We merged approaches of ecological stoichiometry and co-limitation theory, showing how co-limitation reflected shifts in C and P acquisition throughout homeostatic regulation. Increased growth was best explained by elevated consumption rates and improved P assimilation, which both increased with elevated quantity and quality. Notably, C assimilation efficiencies remained unchanged and achieved maximum 18% at low quantity despite pronounced C limitation. Detrital C recalcitrance and substantive post-assimilatory C losses probably set a minimum quantity threshold to achieve positive C balance. Above this threshold, greater quality enhanced larval growth probably by improving P assimilation toward P-intensive growth. We suggest this interplay of C and P acquisition contributes to detritivore co-limitation, highlighting quantity and quality as potential simultaneous bottom-up controls in detrital-based ecosystems, including under anthropogenic change like nutrient enrichment.

Climate change and parasite transmission: how temperature affects parasite infectivity via predation on infective stages

Climate change is expected to affect disease risk in many parasite‐host systems, e.g., via an effect of temperature on infectivity (temperature effects). However, recent studies indicate that ambient communities can lower disease risk for hosts, for instance via predation on free‐living stages of parasites (predation effect). Since general physiological theory suggests predation effects to be temperature‐dependent, we hypothesized that increases in temperature may lead to reduced parasite infectivity via elevated consumption rates of free‐living parasite stages (temperature‐predation interaction). We experimentally investigated such interactions in three marine predators of infective parasite stages. Two species (the oyster Crassostrea gigas, and the barnacle Austrominius modestus) significantly reduced cercarial stages of the trematode Renicola roscovita in mussel hosts (Mytilus edulis), while the third (the crab Hemigrapsus takanoi) did not show a reduction of infective stages at all. In barnacles, cercarial consumption significantly interacted with temperature, with lowest infectivity at highest temperatures. Since these patterns reflected the known thermal responses of the three cercarial predators' feeding rates, parasite consumption rates may be predictable from temperature dependent feeding rates. Our results suggest that integrating temperature‐predation interactions into studies on parasite transmission and on climate change effects is essential and that predators of free‐living stages of parasites may play an important role in indirectly mediating disease risk under climate change.

The environmental effects of salinity and temperature on the oxygen consumption and total body osmolality of the marine flatworm Procerodes littoralis

The present study examined the effect of salinity and temperature on the rate of oxygen consumption and total body osmolality of the triclad turbellarian Procerodes littoralis, a common marine flatworm normally found in areas where freshwater streams run out over intertidal areas. Extremes in environmental factors encountered by P. littoralis were recorded at the study site. These were salinity (0–44 psu), temperature (2.7–24.9 °C) and oxygen concentration (2.8–16.1 mg l −1). Respirometry experiments showed minimal oxygen consumption rates at the salinity extremes encountered by the study species (0 and 40 psu). Further experiments showed relatively constant oxygen consumption rates over the temperature range 5–20 °C and elevated consumption rates at temperatures above 25 °C. Total body osmolality of P. littoralis increased with increasing salinity. The study illustrates how a marine flatworm uses integrated physiological and behavioural mechanisms to successfully inhabit an environment that is predominantly freshwater for up to 75% of the tidal cycle.