Exploring light exposure of hospital nurses working rapidly rotating shifts in relation to sleepiness and sleep

Nightshift work can negatively impact sleep, performance, and health. Careful manipulation of light exposure patterns can help reduce these negative effects but is challenging in conditions of rapidly rotating shiftwork and due to individual differences. As chronotype is related to shiftwork tolerance, we explored patterns of sleep, sleepiness, and light exposure during the first day of nightshift work between earlier and later chronotypes, based on data from an observational field study among rapidly rotating hospital nurses. Due to the limited sample size, only descriptive analyses and visual inspection were conducted. In line with findings of lower shiftwork tolerance, earlier chronotypes (N=6) seemed to be sleepier during work and sleep less than later types (N=7). Differences were also observed in light exposure patterns, revealing potential for light exposure interventions, and suggesting a contribution to shiftwork tolerance. For future intervention studies in aiming to identify a light exposure strategy, our findings highlight the importance of investigating light exposure relative to the individual circadian phase.

Effects of troponoids on mitochondrial function and cytotoxicity

The α-hydroxytropolones (αHT) are troponoid inhibitors of hepatitis B virus (HBV) replication that can target the HBV ribonuclease H (RNase H) with sub-micromolar efficacies. αHTs and related troponoids (tropones and tropolones) can be cytotoxic in cell lines as measured by MTS assays that assesses mitochondrial function. Earlier studies suggest that tropolones induce cytotoxicity through inhibition of mitochondrial respiration. Therefore, we screened 35 diverse troponoids for effects on mitochondrial function, mitochondrial:nuclear genome ratio, cytotoxicity, and reactive oxygen species (ROS) production. Troponoids as a class did not inhibit respiration or glycolysis, although the α-ketotropolone subclass did interfere with these processes. The troponoids had no impact on the mitochondrial DNA to nuclear DNA ratio after three days of compound exposure. Patterns of troponoid-induced cytotoxicity among three hepatic cell lines were similar for all compounds, but three potent HBV RNase H inhibitors were not cytotoxic in primary human hepatocytes. Tropolones and αHTs increased ROS production in cells at cytotoxic concentrations but had no effect at lower concentrations that efficiently inhibit HBV replication. Troponoid-mediated cytotoxicity was significantly decreased upon addition of the ROS scavenger N-acetylcysteine. These studies show that troponoids can increase ROS production at high concentrations within cell lines leading to cytotoxicity, but are not be cytotoxic in primary hepatocytes. Future development of αHTs as potential therapeutics against HBV may need to mitigate ROS production by altering compound design and/or by co-administration with ROS antagonists to ameliorate increased ROS levels.

Telling the Seasons Underground: The Circadian Clock and Ambient Temperature Shape Light Exposure and Photoperiodism in a Subterranean Rodent

Living organisms anticipate the seasons by tracking the proportion of light and darkness hours within a day—photoperiod. The limits of photoperiod measurement can be investigated in the subterranean rodents tuco-tucos (Ctenomys aff. knighti), which inhabit dark underground tunnels. Their exposure to light is sporadic and, remarkably, results from their own behavior of surface emergence. Thus, we investigated the endogenous and exogenous regulation of this behavior and its consequences to photoperiod measurement. In the field, animals carrying biologgers displayed seasonal patterns of daily surface emergence, exogenously modulated by temperature. In the laboratory, experiments with constant lighting conditions revealed the endogenous regulation of seasonal activity by the circadian clock, which has a multi-oscillatory structure. Finally, mathematical modeling corroborated that tuco-tuco’s light exposure across the seasons is sufficient for photoperiod encoding. Together, our results elucidate the interrelationship between the circadian clock and temperature in shaping seasonal light exposure patterns that convey photoperiod information in an extreme photic environment.

Thermoregulatory and Metabolic Demands of Naval Special Warfare Divers During a 6-h Cold-Water Training Dive

Introduction: Extreme environmental conditions induce changes in metabolic rate and substrate use due to thermoregulation. Cold-water full-body submersion for extended periods of time is inevitable for training and missions carried out by Naval Special Warfare divers. Anthropometric, physiologic, and metabolic data have been reported from partial immersion in cold water in non-thermally protected men; data is limited in thermally protected divers in extremely cold water. Thermoregulatory and metabolic demands during prolonged cold-water submersion in Naval Special Warfare divers are unknown.Objective: Assess thermoregulatory and metabolic demands of Naval Special Warfare divers surrounding prolonged cold-water submersion.Materials and Methods: Sixteen active-duty U.S. Navy Sea Air and Land (SEAL) operators tasked with cold-water dive training participated. Divers donned standard military special operations diving equipment and fully submerged to a depth of ∼ 6 m in a pool chilled to 5°C for a 6-h live training exercise. Metabolic measurements were obtained via indirect calorimetry for 10-min pre-dive and 5-min post dive. Heart rate, skin temperature, and core temperature were measured throughout the dive.Results: Core temperature was maintained at the end of the 6-h dive, 36.8 ± 0.4°C and was not correlated to body composition (body fat percentage, lean body mass) or metabolic rate. SEALs were not at risk for non-freezing cold injuries as mean skin temperature was 28.5 ± 1.6°C at end of the 6-h dive. Metabolic rate (kcal/min) was different pre- to post-dive, increasing from 1.9 ± 0.2 kcal/min to 2.8 ± 0.2 kcal/min, p < 0.001, 95% CI [0.8, 1.3], Cohen’s d effect size 2.3. Post-dive substrate utilization was 57.5% carbohydrate, 0.40 ± 0.16 g/min, and 42.5% fat, 0.13 ± 0.04 g/min.Conclusion: Wetsuits supported effective thermoprotection in conjunction with increase in thermogenesis during a 6-h full submersion dive in 5°C. Core temperature was preserved with an expected decrease in skin temperature. Sustained cold-water diving resulted in a 53% increase in energy expenditure. While all participants increased thermogenesis, there was high inter-individual variability in metabolic rate and substrate utilization. Variability in metabolic demands may be attributable to individual physiologic adjustments due to prior cold exposure patterns of divers. This suggests that variations in metabolic adjustments and habituation to the cold were likely. More work is needed to fully understand inter-individual metabolic variability to prolonged cold-water submersion.

Spatial assessment of flow and benefit of tropical cyclone hazard mitigation service

Ecosystems are employed to effectively protect people and communities in coastal areas from tropical cyclone (TC) hazards. Although a spatially explicit TC hazard mitigation service (TCHMS) is essential for devising adaptation strategy and resilience policy, the process and delivery of this program are unclear. We improved a capacity–exposure–demand conceptual framework using Guangdong Province, China, as a case study area, and spatial analysis was employed to assess the ecosystem service. Under this framework, we assessed “capacity” as the natural potential protection against TC hazards, “exposure” as the need for services, and “demand” as the estimated necessity of protecting coastal populations and economic interests. The analysis results were then used to map the TCHMS flow and benefit gap. The results showed that 21.6% of the whole province had low capacity, 25.3% had high exposure, and 19.3% had high demand. A significantly negative correlation was present between the TCHMS capacity and exposure, and a positive correlation was shown between the exposure and demand. In particular, the TCHMS flow and benefit were sufficient in inland areas but were severely deficient in coastal megacities. In Guangdong Province, the Pearl River Delta, and Chaoshan (CS), 3.3%, 4.0%, and 15.3% of the areas showed high demand–low capacity–high exposure patterns, respectively. Our findings will deepen the scientific understanding of the degree of protection a given ecosystem will provide to communities and infrastructures exposed to TC hazards and will thus provide scientific support for coastal ecosystem planning and management.

Decreasing incidence of Acinetobacter baumannii pneumonia and trends in antibiotic consumption: A single-center retrospective observational study

Objective: To describe the epidemiology of Acinetobacter baumannnii (AB) pneumonia at our center, including the antibiotic exposure patterns of individual AB pneumonia cases and to investigate whether hospital-wide antibiotic consumption trends were associated with trends in AB pneumonia incidence. Design: Single-center retrospective study with case-control and ecological components. Setting: US private tertiary-care hospital. Participants and methods: All hospitalized patients with AB infection from 2008 to 2019 were identified through laboratory records; for those with AB pneumonia, medical records were queried for detailed characteristics and antibiotic exposures in the 30 days preceding pneumonia diagnosis. Hospital-wide antibiotic consumption data from 2015 through 2019 were obtained through pharmacy records. Results: Incidence of both pneumonia and nonrespiratory AB infections decreased from 2008 to 2019. Among the 175 patients with AB pneumonia, the most frequent antibiotic exposure was vancomycin (101 patients). During the 2015–2019 period when hospital-wide antibiotic consumption data were available, carbapenem consumption increased, and trends negatively correlated with those of AB pneumonia (r = −0.48; P = .031) and AB infection at any site (r = −0.63; P = .003). Conversely, the decline in AB infection at any site correlated positively with concurrent declines in vancomycin (r = 0.55; P = .012) and quinolone consumption (r = 0.51; P = .022). Conclusions: We observed decreasing incidence of AB infection despite concurrently increasing carbapenem consumption, possibly associated with declining vancomycin and quinolone consumption. Future research should evaluate a potential role for glycopeptide and quinolone exposure in the pathogenesis of AB infection.