Maintenance of alertness and performance by a brief nap after lunch under prior sleep deficit

We examined the effects of a 15-min nap after lunch on subsequent alertness, performance, and autonomic function following a short sleep the preceding night. Subjects were 12 healthy students who had slept for only 4 hours the night before being tested. They experienced both nap and no-nap conditions in a counterbalanced order, at least a week apart. The nap condition included a 15-min nap opportunity (12:30-12:45) in bed with polygraphic monitoring. We measured the P300 event-related potential, subjective sleepiness (Visual Analog Scale), and electrocardiogram (ECG) at 10:00, 13:15, and 16:15, and task performance (logical reasoning and digit span) at 10:00, 11:30, 13:15, 14:45, 16:15, and 17:45. Mean home sleep measured by actigraphy was 3.5 hours under both conditions. At 13:15, the P300 latency after the nap was significantly shorter than after no nap, but its amplitude was not affected by napping. Subjective sleepiness at 13:15 and 14:45 was significantly lower, and accuracy of logical reasoning at 13:15 was significantly higher after the nap than after no nap. No other performance measures or the ECG R-R interval variability parameters differed significantly between the nap and no-nap conditions. Mean total sleep time during the nap was 10.2 min, and no stage 3 and 4 sleep was observed. The above results suggest that under prior sleep deficit, a 15-min nap during post-lunch rest maintains subsequent alertness and performance, particularly in the mid-afternoon.     

Suppression of electroencephalogram Δ power density during non-rapid eye movement sleep as a result of a prolonged cognitive task prior to sleep onset

The effects of a prolonged cognitive task prior to sleep onset on subsequent sleep patterns were examined in 14 healthy subjects who were randomly assigned to two conditions. Those assigned to a working condition were asked to engage in a prolonged cognitive task until close to bedtime (0200 hours), whereas those assigned to a relaxing condition were instructed to perform the same task during the daytime and then to stay awake in a relaxed state until the same bedtime as the work group. Visual scoring of sleep stages showed no significant differences in the amounts of stage 4 and slow wave sleep (stage 3+4) between the two conditions. Power spectrum analysis of sleep electroencephalogram (EEG) revealed that the EEG (0.5–4.0 Hz) power density in the first non-rapid eye movement (REM)-REM sleep cycle was significantly lower following the prolonged cognitive task prior to sleep onset than following the relaxed wakefulness and that the decreased EEG power density in the first sleep cycle was not compensated for during the later part of the sleep. These findings would indicate that the prolonged cognitive task prior to sleep onset may suppress EEG power density during subsequent sleep, suggesting that such a task may interfere with the development of deep non-REM sleep.     

A new model rat with acute bronchiolitis and its application to research on the toxicology of inhaled particulate matter

The aim of the present study was to establish a useful animal model that simulates humans sensitive to inhaled particulate matter (PM). We have developed a new rat model of acute bronchiolitis (Br) by exposing animals to NiCl2 (Ni) aerosols for five days. Three days following the Ni exposure, the animals developed signs of tachypnea, mucous hypersecretion, and bronchiolar inflammation which seemed to progress quickly during the fourth to fifth day. They recovered from lesions after four weeks in clean air. To assess the sensitivity of the Br rats to inhaled particles, two kinds of PM of respirable size were tested with doses similar to or a little higher to the recommended threshold limit values (TLVs) for the working environment in Japan. Titanium dioxide (TiO2 = Ti) was chosen as an inert and insoluble particles and vanadium pentoxide (V2O5 = V), as a representative soluble and toxic airborne material. The Br rats exposed to either Ti or V were compared the pathological changes in the lungs and the clearance of particles to those in normal control or Br rats kept in clean air. The following significant differences were observed in Br rats: 1. delayed recovery from pre-existing lesions or exacerbated inflammation, 2. reductions in deposition and clearance rate of inhaled particles with the progress of lesions. The present results suggest that Br rats are more susceptible to inhaled particles than control rats. Therefore, concentrations of particulate matter lower than the TLVs for Japan, which have no harmful effects on normal lungs, may not always be safe in the case of pre-existing lung inflammation.     

Laboratory measurement of hazardous fumes and gases at a point corresponding to breathing zone of welder during a CO2 arc welding

Concentrations of fumes, ozone (O3), carbon monoxide (CO), nitric oxide (NO), manganese (Mn) and total and hexavalent chromium (Cr) as well as size distribution of fumes were measured at a point corresponding to the welder's breathing zone during CO2-arc welding, using a welding robot and three kinds of wires. Concentrations of fumes, O3, CO, Mn and total-Cr were found to exceed their corresponding occupational exposure limit (OEL) values, while the concentrations of NO and Cr(VI) were below those OEL levels. Airborne concentration of Mn exceeded its OEL value, and the Mn content was 8 times higher in welding fumes than in the wire. Using an additive equation of OEL and exposure concentration of each hazardous component, health risk in welders with combined exposure to welding fumes and gases was assessed as 18.6 to 46.0 times of OEL, which exceeded the unity. This finding suggests that effective protection of welders from the exposure can be attained by use of the supplied-air respirator or combined use of a dust respirator and a local exhaust system.     

SARS-CoV-2 Disinfection of Air and Surface Contamination by TiO2 Photocatalyst-Mediated Damage to Viral Morphology,RNA, and Protein

SARS-CoV-2 is the causative agent of COVID-19, which is a global pandemic. SARS-CoV-2 is transmitted rapidly via contaminated surfaces and aerosols, emphasizing the importance of environmental disinfection to block the spread of virus. Ultraviolet C radiation and chemical compounds are effective for SARS-CoV-2 disinfection, but can only be applied in the absence of humans due to their toxicities. Therefore, development of disinfectants that can be applied in working spaces without evacuating people is needed. Here we showed that TiO₂-mediated photocatalytic reaction inactivates SARS-CoV-2 in a time-dependent manner and decreases its infectivity by 99.9% after 20 min and 120 min of treatment in aerosol and liquid, respectively. The mechanistic effects of TiO₂ photocatalyst on SARS-CoV-2 virion included decreased total observed virion count, increased virion size, and reduced particle surface spike structure, as determined by transmission electron microscopy. Damage to viral proteins and genome was further confirmed by western blotting and RT-qPCR, respectively. The multi-antiviral effects of TiO₂-mediated photocatalytic reaction implies universal disinfection potential for different infectious agents. Notably, TiO₂ has no adverse effects on human health, and therefore, TiO₂-induced photocatalytic reaction is suitable for disinfection of SARS-CoV-2 and other emerging infectious disease-causing agents in human habitation.     

Partial insomnia, hyperactivity and hyperdipsia induced by repeated administration of toluene in rats: their relation to brain monoamine metabolism

In an attempt to examine chronic effects of toluene on sleep, spontaneous locomotor activity and drinking behavior, rats were repeatedly administered toluene i.p. at doses of 100 and 200 mg/kg body weight for 14 consecutive days. The 200-mg/kg injections induced a decrease in total sleep on Day 1, an increase in locomotor activity on Days 1 through 4 and an increase in drinking activity on Days 0 through 6 after discontinuation of the daily injections. Both the reduced sleep and the increased locomotor activity appeared during the light period, whereas the drinking activity increased during the dark period. In order to find neurochemical correlates of the toluene-induced changes in behavior, regional concentrations of brain monoamines and their metabolites were determined. The toluene-induced partial insomnia and hyperactivity were associated with lowered concentrations of serotonin in frontal cortex, hippocampus and midbrain and 5-hydroxyindoleacetic acid in midbrain and hypothalamus. The increased drinking activity was associated with increased concentrations of striatal 3,4-dihydroxy-phenylacetic acid and homovanillic acid and hypothalamic noradrenaline and 3-methoxy-4-hydroxyphenylethyleneglycol. Central monoaminergic mechanisms were implicated in the toluene-induced partial insomnia, hyperactivity and hyperdipsia.     

Carcinogenicity and chronic toxicity after inhalation exposure of rats and mice to N,N-dimethylformamide

Carcinogenicity and chronic toxicity of N,N-Dimethylformamide (DMF) were examined by inhalation exposure of groups of 50 rats and 50 mice of both sexes to DMF vapor at a concentration of 0, 200, 400 or 800 ppm (v/v) for 6 h/d, 5 d/wk, for 104 wk. In rats, incidences of hepatocellular adenomas and carcinomas significantly increased in the 400 and 800 ppm-exposed groups and in the 800 ppm-exposed group, respectively. The hepatocellular adenoma did not increase significantly in the 400 ppm-exposed female rats, but its incidence exceeded a range of historical control data in the Japan Bioassay Research Center (JBRC). In mice, incidences of hepatocellular adenomas and carcinomas significantly increased in all the DMF-exposed groups. Incidence of hepatoblastomas significantly increased in the 200 and 400 ppm-exposed male mice, and 4 cases of hepatoblastomas in the 400 ppm-exposed female mice and the 800 ppm-exposed male mice exceeded the range of historical control data of the JBRC. Incidences of altered cell foci increased in the liver of exposed rats and mice in an exposure concentration-related manner, and those foci were causally related to the hepatocellular tumors. Liver weights increased in both rats and mice exposed to DMF at 200 ppm and above. Increased levels of gamma-GTP, ALT, AST and total bilirubin in exposed rats of both sexes and AST and ALT in exposed mice of both sexes were noted. It was concluded that 2-yr inhalation exposure to DMF increased incidences of hepatocellular adenomas and carcinomas in rats and incidences of hepatocellular adenomas, carcinomas and hepatoblastomas in mice, and that hepatocarcinogenicity of DMF was more potent in mice than in rats.