Delayed sleep-wake rhythm due to staying at home during the COVID-19 pandemic and sleep debt after returning to campus among Japanese nursing university students: A longitudinal study.

This study aimed to investigate sleep problems during staying at home due to the coronavirus disease 2019 (COVID-19) pandemic and after returning to campus among university nursing students. We analyzed data from self-reported sleep surveys conducted during a nursing course at a university in Tokyo between 2019 and 2021. During staying at home due to COVID-19, we observed delayed sleep-wake rhythm, prolonged sleep duration on weekdays, a decreased sleep debt, improved daytime sleepiness, and worsened insomnia, especially in terms of difficulty initiating sleep (Study 1; 18 paired data).

Investigation of errors by radiological technologists and evaluation of preventive measures: general and mobile X-ray examinations.

The first objective in this study was to identify the errors of incidents and accidents that occurred in general and mobile X-ray examinations. Based on the analysis of results, the second purpose in this study was to propose useful measures to prevent such errors. As much as 553 radiological technologists in the Gunma Prefecture were surveyed on their experience with errors related to general and mobile X-ray examinations.

Report from the in vitro micronucleus assay working group.

Unlabelled: At the Washington "2nd International Workshop on Genotoxicity Testing" (25-26 March 1999) current methodologies and data for the in vitro micronucleus test were reviewed. As a result, guidelines for the conduct of specific aspects of the protocol were developed. Agreement was achieved on the following topics: choice of cells, slide preparation, analysis of micronuclei, toxicity, use of cytochalasin-B, number of doses, and treatment/harvest times [Environ.

Establishment and characterization of three new rat renal cell carcinoma cell lines from N-ethyl-N-hydroxyethylnitrosamine-induced basophilic cell tumors.

Three new rat cell lines (designated as BP13, BP30 and BP36B), derived from rat basophilic-type renal cell carcinomas induced with N-ethyl-N-hydroxyethylnitrosamine, were established and characterized. Passaged up to 100 times in vitro for 3 years, each cell line forms epithelial monolayers with cell cycles for BP13, BP30 and BP36B of 29, 21 and 17 h, respectively. Positive glucose-6-phosphate dehydrogenase (G6PD) and gamma-glutamyltransferase (gamma-GT) activity in their cytoplasm, but negative succinate dehydrogenase (SD) and slightly positive carbonic anhydrase type II (CA) localization indicates an origin from proximal tubules.

Report from the In Vitro Micronucleus Assay Working Group.

At the Washington International Workshop on Genotoxicity Test Procedures (March 25-26, 1999), the current methodologies and data for the in vitro micronucleus test were reviewed. From this, guidelines for the conduct of specific aspects of the protocol were developed. Because there are a number of important in vitro micronucleus validation studies in progress, it was not possible to design a definitive, internationally harmonized protocol at this time.

Apoptosis during iron chelator-induced differentiation in F9 embryonal carcinoma cells.

We have previously demonstrated that three potent iron chelators, hinokitiol, dithizone and deferoxamine, induce differentiation of F9 embryonal carcinoma cells, as do other well-known morphogens such as retinoic acid (RA) and sodium butyrate (NaB). In this study, we compared the patterns of cell proliferation, cell death and cell cycle arrest during the process of differentiation induced by these five agents. When F9 cells were cultured with the agents at their individual differentiation-inducing concentrations, cell proliferation was rapidly inhibited by treatment with the iron chelators and NaB.

Validation study of the in vitro micronucleus test in a Chinese hamster lung cell line (CHL/IU).

We conducted a collaborative validation study, under the auspices of the Japanese Ministry of Labour, on the in vitro micronucleus test to see if it could be used as an alternative to the in vitro chromosome aberration test for evaluation of chemical safety. We used the Chinese hamster lung cell line (CHL/IU), which is the most widely used system for the latter test in Japan, and evaluated 66 chemicals, including clastogens and polyploidy inducers. The cytochalasin B cytokinesis blocking method, which is commonly used in human lymphocyte culture, was applied to the established cell line, but did not improve the detection of chemically-induced micronuclei in continuously growing cells.

Application of laser scanning cytometry to the analysis of chromosomal aberrations induced by benzo[a]pyrene in CHO-WBLT cells.

Background: A recently developed laser scanning cytometry technique was applied to cytometric studies to detect rapidly stable chromosomal aberrations induced by a carcinogen in a Chinese hamster fibroblast cell line, CHO-WBLT.

Methods: Individual chromosomes were collected from metaphase cells by a syringe technique and spread on slides. The DNA content of each chromosome stained with propidium iodide was measured with a laser scanning cytometer (LSC).

Chromosome aberration assays in genetic toxicology testing in vitro.

The chromosome aberration test using cultured mammalian cells is one of the sensitive methods to predict environmental mutagens and/or carcinogens, and is a complementary test to the Salmonella/microsome assay (Ames test). From our recent survey of 951 chemicals which have been tested for their clastogenicity in cultured mammalian cells such as Chinese hamster fibroblasts or human lymphocytes, it was noted that 47% of them are consistently positive either with or without metabolic activation. When the test was performed using the cell line CHL/IU, 39.

Multilaboratory comparison of in vitro tests for chromosome aberrations in CHO and CHL cells tested under the same protocols.

Different test results have been reported for the same chemicals in two in vitro chromosome aberration test systems, CHL cells tested by a Japanese protocol and CHO cells tested by the US National Toxicology Program [Sofuni et al., Mutat Res 241:173-213,1990]. Here, laboratories in Japan, the US and the UK tested 9 such chemicals in CHL and CHO cells using the same protocols and found all 9 positive in both cell types; differences in earlier conclusions with these chemicals were due mainly to test protocol, not to different sensitivities of the cells.

The possible role of acetyltransferase in the induction of cytogenetic effects by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in cultured Chinese hamster cells.

When metabolically activated, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine isolated from cooked food, is clastogenic in cultured Chinese hamster and human cells. Secondary metabolites of PhIP are formed via acetyltransferase (AT) and sulfotransferase (ST) activity; however, which is responsible for its clastogenic effect is unknown. We addressed this question.

Evaluation of the genotoxicity of stevioside and steviol using six in vitro and one in vivo mutagenicity assays.

Stevioside, a constituent of Stevia rebaudiana, is commonly used as a non-caloric sugar substitute in Japan. The genetic toxicities of stevioside and its aglycone, steviol, were examined with seven mutagenicity tests using bacteria (reverse mutation assay, forward mutation assay, umu test and rec assay), cultured mammalian cells (chromosomal aberration test and gene mutation assay) and mice (micronucleus test). Stevioside was not mutagenic in any of the assays examined.

Re-evaluation of chromosomal aberration induction on nine mouse lymphoma assay "unique positive' NTP carcinogens.

In a collaborative study organized under the JEMS MMS, nine mouse lymphoma assay (MLA) "unique positive' NTP rodent carcinogens were re-evaluated by an in vitro chromosomal aberration assay using Chinese hamster lung fibroblast cells (CHL/IU). Six of nine chemicals induced chromosomal aberrations; bromodichloromethane, chlorendic acid and isophorone induced structural aberrations, and chlorodibromomethane, pentachloroethane and 1,1,1,2-tetrachloroethane induced numerical aberrations (polyploidy). These six chemicals, therefore, are not uniquely positive in the MLA.

Cytogenetic effects of a food mutagen, 2-amino-1-methyl-6-phenylimidazo[4,5-beta]pyridine (PhIP), and its metabolite, 2-hydroxyamino-1-methy-6-phenylimidazo[4,5-beta]pyridine (N-OH-PhIP), on human and Chinese hamster cells in vitro.

2-Amino-1-methyl-6-phenylimidazo[4,5-beta]pyridine (PhIP) induced structural chromosomal aberrations (CAs) and sister-chromatid exchanges (SCEs) in human lymphocytes and human diploid fibroblasts (TIG-7) at concentrations above 12.5 microgram /ml in the presence of rat S9 mix. PhIP also elevated the frequencies of SCEs in human lymphocytes in the presence of rat S9 at concentrations above 2.

Report from working group on in vitro tests for chromosomal aberrations.

The following summary represents a consensus of the working group except where noted. The items discussed are listed in the order in which they appear in the OECD guideline (473) for easy reference. Metabolic activation.

2-Amino-3-methylimidazo[4,5-f]quinoline (IQ), a carcinogenic pyrolysate, induces chromosomal aberrations in Chinese hamster lung fibroblasts in vitro.

The ability of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) to induce chromosomal aberrations (CAs) in Chinese hamster lung fibroblast (CHL/IU) cells in vitro was examined. On incubation with rat S9 (2.5-10%, v/v) for 3 h, followed by a recovery culture period of 21 h, IQ caused significant induction of CAs at a concentration 20 micrograms/ml, but had less effect at 40 micrograms/ml.

Regulation of G418 selection efficiency by cell-cell interaction in transfection.

We attempted to establish the optimum conditions for the calcium phosphate (CaPO4) precipitation protocol by counting G418 resistant (G418r) colonies after transfection of pSV2-neo DNA into BALB 3T3 cells. The amount and molecular size of carrier DNA, number of plating cells, treatment period of DNA-CaPO4 precipitates and expression time of G418 selection were found to be important factors in the induction of G418r colonies. Six G418r clones were derived from BALB 3T3, NIH 3T3 and FRSK cells, and cocultured with G418 sensitive (G418s) parent cells in G418 medium.

A sensitive umu test system for the detection of mutagenic nitroarenes in Salmonella typhimurium NM1011 having a high nitroreductase activity.

A sensitive umu test system for the detection of mutagenic nitroarenes has been developed using a new tester strain Salmonella typhimurium NM1011 having a high nitroreductase activity. The new strain was constructed by subcloning the bacterial nitroreductase gene into a plasmid pACYC184 and introducing the plasmid into the original strain S. typhimurium TA1535/pSK1002 harboring a fusion gene umuC'-'lacZ (pSK1002).

Flow cytometric micronucleus test with mouse peripheral erythrocytes.

Flow cytometric (FC) analysis was applied to micronucleus test with mouse peripheral blood erythrocytes. The method is based on the measurement of peak fluorescence (PFL) of sphered glutaraldehyde-fixed erythrocytes before and after staining with 4',6-diamidino-2-phenylindole (DAPI), in an EPICS V flow cytometer. The frequency of micronucleated erythrocytes (MNEs) is calculated by a computer program comparing PFL data obtained with and without DAPI.

Mouse bone marrow micronucleus test using flow cytometry.

At present, the micronucleus test is the most popular short-term assay for the in vivo detection of clastogens or spindle poisons. As micronuclei are rare events, it has been argued that the conventional microscopical analysis based on 500-2000 cells per animal does not provide enough sensitivity. In addition, the manual scoring of micronuclei is time-consuming and tedious.

The expert system for toxicity prediction of chemicals based on structure-activity relationship.

The prediction systems of chemical toxicity has been developed by means of structure-activity relationship based on the computerized fact database (BL-DB). Numbers and ratio of elements, side chains, bonding, position, and microenvironment of side chains were used as structural factors of the chemical for the prediction. Such information was obtained from the BL-DB database by Wiswesser line-formula chemical notation.

Decreased clastogenicity of dinitropyrenes in Chinese hamster lung (CHL) subclone cells with low NADPH-cytochrome P-450 reductase activity.

Clastogenic potentials of 1,3-, 1,6- and 1,8-dinitropyrenes (DNPs) were compared between Chinese hamster lung (CHL) cells and its subclone MM1 cells, which were recently isolated as menadione-resistant cells after treatment with MNNG. NADPH-cytochrome P-450 reductase activity of the MM1 cells decreased to 50% of that in the parental CHL cells. All 3 DNPs induced chromosomal aberrations without exogenous metabolic activation systems in the CHL cells.

Mutagenicity of wood smoke condensates in the Salmonella/microsome assay.

Smoke condensates of woods used for food preservation and aromatization in Nigeria were tested for mutagenic activity using Salmonella typhimurium TA98 and TA100. The woods were: white mangrove (Avicennia nitida), red mangrove (Rhizophora racemosa), mahogany Khaya sp.), abura (Mitragyna ciliata), alstonia (Alstonia boonei) and black afara (Terminalia ivorensis).