Reactive oxygen species (ROS) generated by environmental chemicals can cause sequence-specific DNA damage, which may lead to carcinogenesis and aging. We investigated the mechanism of DNA damage by environmental chemicals (catechol, propyl gallate and bisphenol-A), homocysteine and UVA radiation using human cultured cell lines and ³²P-labeled DNA fragments. Carcinogenic catechol induced piperidine-labile sites frequently at thymine residues in the presence of Cu(II) and NADH. Furthermore, catechol increased the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a characteristic oxidative DNA lesion, in human leukemia cell line HL-60, but not in HP100, a hydrogen peroxide (H₂O ₂)-resistant cell line derived from HL-60. Thus, it is concluded that oxidative DNA damage through generation of H₂O ₂ plays an important role in the carcinogenic process of catechol. In addition, an environmental factor, bisphenol-A, and a dietary factor, propyl gallate, also induced sequence-specific DNA damage via ROS generation.
UVA, as well as UVB, contributes to photoaging. In humans, telomere shortening is believed to be associated with cell senescence. In this study, we investigated the shortening rate of telomeres in human WI-38 fibroblasts exposed to UVA irradiation. The telomere length (as measured by terminal restriction fragment length) in WI-38 fibroblasts irradiated with UVA decreased with increasing the irradiation dose. UVA irradiation with riboflavin caused damage specifically at the GGG sequence in the DNA fragments containing telomere sequence (TTAGGG)₄. We concluded that the GGG-specific damage in telomere sequence induced by UVA irradiation participates in the increase of the telomere shortening rate.
In this report, we show our experimental results and discuss the mechanisms of sequence-specific DNA damage in relation to carcinogenesis and aging.

View full abstract

Inactivation of the p16^INK4a gene is one of the most frequent defects that contribute to oncogenesis in human cancer, since it is a tumor-suppressor gene. Therefore, functional restoration of p16^INK4a is one of the most effective methods for cancer prevention. We proposed the concept of ‘gene-regulating chemoprevention’ and ‘molecular-targeting prevention’ of cancer, which assumes that transcriptional regulation by drugs on tumor-suppressor genes or functionally similar genes to the tumor-suppressor genes contributes to the prevention of human malignancies. The p16^INK4a homologs p15^INK4b, p18^INK4c and p19^INK4d have been recently identified, and these four members constitute the INK4 family of proteins. All directly bind to cyclin D-cyclin dependent kinase (CDK) 4/6 and are therefore specific inhibitors of these complexes. We recently showed that histone deacetylase (HDAC) inhibitors, promising chemopreventive and chemotherapeutical agents, induce p15^INK4b and p19^INK4d gene expression and cause growth arrest, suggesting that both genes are important molecular targets for HDAC inhibitors. Furthermore, we found that 12-O-tetradecanoylphorbol-13-acetate (TPA), which is widely used as a tumor promoter and protein kinase C activator, promotes human cancer cell growth through the down-regulation of p18^INK4c gene expression. This suggests that a mouse two-stage carcinogenesis model using TPA might partially represent the most common human carcinogenesis pathway related to RB. Our results suggest that the INK4 family consists of attractive and promising molecular targets for the ‘gene-regulating chemoprevention’ and ‘molecular-targeting prevention’ of cancer.

View full abstract

Objective: The food consumption and serum nutritional status of people living in the Kathmandu valley, Nepal, were examined to obtain actual data for comparison with our previous findings.
Methods: A dietary survey of 45 males and 60 females was carried out in March 1997 by the 24-hr dietary recall method and nutrient intake was calculated from food tables of India and Japan. Fasting venous blood samples were obtained and serum biochemical parameters were measured using clinical kits.
Results: The mean body mass index value was at about the same level in both sexes, although the mean percentage body fat of females was higher than that of males, and vice versa for packed red cell volume. The main foods consumed by both sexes, were rice, potatoes, meats, milk & dairy products and vegetables, with a difference in the amounts consumed. Females did not drink alcoholic beverages. The mean daily intakes of energy, protein, lipids, iron and vitamin B group for the males were higher than those for the females, while those of vitamins A and C for the males were lower than those for the females. The mean values of serum biochemical parameters for both sexes were generally at the normal levels, but those of ALT and TG were at the higher end of the normal range. Differences of correlation between food groups and between serum parameters were observed depending on the sex, however, no clear relationship between food and nutrient intake and serum biochemical parameters were observed.
Conclusions: The present food intake study revealed that the amounts of food consumption for both sexes, especially for the females, were mostly insufficient although the serum parameters were at the normal levels. The energy intake of both sexes was lower than that of estimated requirements and those in Terai region. The relatively high serum TG level of the subjects may be due to the consumption of large amounts of cereals containing much carbohydrate. Our findings suggested a marked influence on food consumption by food price and income in spite of the easier food availability in the city, and also lack of knowledge about nutrients and health, thus there is need for improvement of the nutritional status of this group of people.

View full abstract

Objectives: To clarify the origin of dioxin and related compounds (dioxins) in human hair, we determined the amounts of adsorbed dioxins in human hair, and the distribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rats.
Methods: Human hair specimens, packed in a glass column, were exposed to ambient air that was introduced into the column with an air pump for 24 h. Rats were administered TCDD by gavage at doses of 0.2, 0.8, and 1.6 μg/kg body weight. Four weeks after TCDD administration, hair from the back, serum, and adipose tissue were removed under diethyl ether anesthesia. The amounts of dioxins in these samples were analyzed by high resolution gas chromatography with mass spectroscopy.
Results: Exposure of the hair specimens to ambient air for one day increased the total toxic equivalent (TEQ) value by 51%. In TCDD-treated rats, the amount of TCDD in hair increased in a dose-dependent manner, and showed a significant positive correlation with that in adipose tissue.
Conclusions: Human hair was found to retain dioxins by both internal and external exposure, and the contribution of external exposure was estimated to be about 40% of the TEQ.

View full abstract

Objectives: To analyze actual conditions of the quality of life (QOL) in junior high school students, we developed a questionnaire based on the PRECEDE-PROCEED model, and we conducted a survey by using this questionnaire.
Methods: We conducted a workshop organized with 29 specialists on school health and community health to develop the questionnaire. The QOL outcome was assessed by the QOL Profile-Adolescent Version (QOLPAV). The subjects of the questionnaire surveys were 1600 general students in four junior high schools. To investigate a correlation between QOLPAV, behaviors and three enhancing factors, two different multiple regression models were constructed.
Results: The question battery for QOLPAV was found to be a high value of Chronbach’s α. Among present subjects, 16.5% were categorized as “problematic” or “very problematic” classified by QOLPAV scores. In the first multiple regression model, significantly high odds ratios were obtained between the QOLPAV and 4 questions for behaviors, such as “studying with high motivation” (OR 1.64), “getting along well with my friends” (2.72), “having things I am interested in” (1.70), and “making my own decisions” (1.80). In the second model, significantly high odds ratios were obtained commonly between the above 4 questions about behaviors and 2 questions on enabling factors, such as “easy to understand lessons” (1.32-1.71) and “speaking to friends easily” (1.30-3.22).
Conclusions: 1) We developed a questionnaire to analyze the actual condition of QOL in junior high school students with sufficient validity and availability. 2) Among the present subjects, 16.5% were found to be problematic QOLPAV. 3) Among the factors of behaviors, those representing positive willing and high coping ability with the elements of each school life contributed significantly to the QOLPAV. And among enhancing factors, “enabling factors” and “reinforcing factors” were stronger contributors to the behaviors strongly related to the QOLPAV than that of “predisposing factors”.

View full abstract

In contrast to selenoprotein Ps (SelPs) from other animal species, bovine selenoprotein P-like-protein (SelPLP) was found to contain a tandem repeat of (CAYYCC)₁₁. During an investigation into whether SelPLP was a bovine substitute for SelP or uniquely bovine, its mRNA was found to consist of multiple variants with different length tandem repeat, namely p(0) with (CAYYCC)₁₁, p(-4) lacking (CAYYCC)₄, p(-8) lacking (CAYYCC)₈, and p(-9) lacking (CAYYCC)₉. Although they were encoded on a single gene locus, neither classical GT-AG nor minor class AT-AC donator-acceptor sequences for alternative splicing were identified. A subsequent S1 protection assay using oligonucleotides, whose sequence may occur as variants, performed against bovine poly(A)⁺RNA identified a total of nine variants. Judging from the sequence of these variants and the branch point mapping, the consensus sequence for recognition of the donator was CACCCCCAC and of the acceptor and the branch point A nucleotide, ACCCCCAT or ACCCCCATCCCCAT. Furthermore, when the p(0) insert mRNA was expressed in COS-7 cells derived from an African green monkey kidney, cDNAs corresponding to p(-8) and p(-9) could be isolated. Therefore, the bovine SelPLP mRNAs consisted of multiple variants probably due to a novel splicing mechanism which was not bovine-specific but common to other mammals.

View full abstract

Objectives: The toxicity of microglass fibers (MG), one of the man-made mineral fibers, has not been sufficiently evaluated. The aim of the current study was to evaluate the cytotoxicity of MG in vitro.
Methods: Alveolar macrophages were obtained from the bronchoalveolar lavage of male F344/N rats. The macrophages were exposed to MG at concentrations of 0, 40, 80, 160 and 320 μg/ml. The effects of MG on the macrophages were examined by cell magnetometry, LDH assay and morphological observation.
Results: In the cell magnetometry experiment, a significant delay of relaxation (the reduction of remanent magnetic field strength) was observed in the cells treated with 160 and 320 μg/ml of MG in a dose-dependent manner. A significant increase in LDH release was also observed in the cells with 160 and 320 μg/ml in a dose-dependent manner. Changes in the cytoskeleton were observed after exposure to MG, by immunofluorescent microscopy using an α-tubulin antibody.
Conclusions: The cytotoxicity of MG on alveolar macrophages was demonstrated with cell magnetometry. The mechanism of the toxic effects of MG was related to cytoskeleton damage.

View full abstract