The nematode

Caenorhabditis

(C. elegans) was used for a multiple-generation toxicity bioassay of phenols. We examined the sublethal toxicity (fecundity and reproduction) of bisphenol A (BisA), 4-(1-adamantyl) phenol (Adp), and 4,4′-(1,3-adamantanediyl) diphenol (AdDP) over five generations using a Nematode Growth Medium (NGM) 1.7% agar plate. In the fourth generation, the phenols affected the fecundity rate of C. elegans at doses 100- to 10000-fold lower than the LC₅₀s. In particular, at 1 nM BisA, the number of worms decreased significantly to about 50% of control (p < 0.05). A comparison of the number of viable worms and eggs suggested that the phenols exert hatching toxicity. In addition, individuals with an abnormality in the vulva, which could not ovulate, appeared on the phenol-containing plates. We confirmed that phenols disrupt reproduction in C. elegans and that the method using NGM agar plates facilitates multi-generational toxicity tests of chemicals that are poorly soluble in water.

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To evaluate the toxicity of environmental chemicals to invertebrates, a static bioassay was developed in the laboratory using the

Caenorhabditis

(C. elegans). First, reproducibility of this aquatic acute toxicity test system was confirmed. In order to estimate chemical toxicities in C. elegans, worms were subsequently exposed to eleven different xenobiotics. Mortality after 24 hr was adopted as the endpoint of toxicity. We found that benzo[a]pyrene, nonylphenol, benzophenone, bisphenol A and cadmium chloride affected viability of C. elegans. These data suggest that C. elegans is a suitable toxicity test organism for environmental xenobiotic chemicals, and that lethality can be used as a testing endpoint.

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細菌食性の土壌線虫である

Caenorhabditis

(線虫)が，ヒト病原体の代替宿主として認められつつある．本研究の目的は，食中毒細菌が線虫に病原性を示すか否か検討することにある．ペプトンを含まない寒天上に各種の病原細菌を塗りつけた後，若い成虫を移して摂取させた．24時間ごとに線虫の生死を確認し，生残率を経時的に調べた．供試した14種の病原体のうちセレウスと腸管侵入性大腸菌を除く12菌種(各種下痢原性大腸菌，黄色ブドウ球菌，腸炎ビブリオ，サルモネラ，リステリア，エロモナス，エルシニア)が，線虫の生残率を対照群に比べて有意に低下させた．既に報告されたペプトンを含む寒天上で実施された線虫の感染実験と同様に，線虫に病原性を示す菌は，ペプトンを含まない寒天上でも線虫に感染し，その体内で増殖していることが明らかとなった．しかしながら，ヒトに病原性を示さない大腸菌HS株や，マウスに対する病原性を失ったリステリアの変異株が線虫に病原性を示した．線虫は食中毒菌の病原性を検討するうえで有用であるが，線虫に対する病原性がヒトへの腸管病原性を必ずしも反映するわけではない．線虫を代替宿主として利用するに当たっては，病原菌の種類や解析する病原遺伝子を注意深く選定し実験することが求められる．

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In this paper,

Caenorhabditis

(C. elegans) is proposed as a model organism for studying chemical effects over multiple generations. We investigated whether C. elegans responds to vertebrate steroid hormones. We found that estrogenic steroids, especially estradiol (E2), have a cholesterol-like potency in supporting the reproduction of C. elegans. In contrast, testosterone (TS) and diethylstilbestrol (DES) did not display this potency. On the other hand, E2, TS and DES supressed the fecundity rate of C. elegans, when culture carried out with cholesterol. Moreover effect of TS accumulated over generation, in contrast to the other chemicals tested. These data suggested that with convenient biomarkers such as fecundity, C. elegans might be an effective model organism for studying chemical actions, including the disruption of reproduction.

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The study of radiation effect in Caenorhabditis (C.) elegans has been carried out over three decades and now allow for understanding at the molecular, cellular and individual levels. This review describes the current knowledge of the biological effects of ionizing irradiation with a scope of the germ line, aging and behavior. In germ cells, ionizing radiation induces apoptosis, cell cycle arrest and DNA repair. Lots of molecules involved in these responses and functions have been identified in C. elegans, which are highly conserved throughout eukaryotes. Radiosensitivity and the effect of heavy-ion microbeam irradiation on germ cells with relationship between initiation of meiotic recombination and DNA lesions are discussed. In addition to DNA damage, ionizing radiation produces free radicals, and the free radical theory is the most popular aging theory. A first signal transduction pathway of aging has been discovered in C. elegans, and radiation-induced metabolic oxidative stress is recently noted for an inducible factor of hormetic response and genetic instability. The hormetic response in C. elegans exposed to oxidative stress is discussed with genetic pathways of aging. Moreover, C. elegans is well known as a model organism for behavior. The recent work reported the radiation effects via specific neurons on learning behavior, and radiation and hydrogen peroxide affect the locomotory rate similarly. These findings are discussed in relation to the evidence obtained with other organisms. Altogether, C. elegans may be a good "in vivo" model system in the field of radiation biology.

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We describe a novel approach to evaluating the respiratory toxicity of chemicals in the free-living nematode

Caenorhabditis

. Using DOX-96KT, a general purpose, multi-channel dissolved oxygen (DO) measuring system, we measured the DO concentration in culture media containing C. elegans exposed to chemicals to assay for respiratory toxicity. The current value, which is an index of the dissolved oxygen concentration in culture media, was measured every 10 sec for 30 min at 24°C. We focused on the respiration levels of the exposed worms between 500 and 1800 sec. This method produces results that are similar to the computer tracking system measuring behavioral toxicity. Since it can do multiple dilution series tests at a given time, it is useful for concentration-activity correlation studies. This novel technique is not only an alternative to the computer tracking system for measuring behavioral toxicity but also a rapid sublethal toxicity test for chemical hazard assessment.

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We observed and evaluated the feeding behavior of the free-living nematode

Caenorhabditis

(C. elegans) after exposure to bisphenol A (BPA) and nonylphenol (NP). Exposed organisms were transferred to chemical-free culture medium and their attainment levels (the number of worms reaching the food source divided by the total number of worms on the Petri plate) were recorded after 2, 4, 6, 8, and 24 hr. Results showed a significant decrease in the attainment level of worms exposed to 10 μM and 0.1 μM BPA. However, there was a slight increase in the attainment level of nematodes treated with 1 μM NP. These results differ from previous studies showing NP as being more lethal to nematodes than BPA.

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Toxicity studies using the nematode

Caenorhabditis

(C. elegans) as a model organism have shown that perfluoro organic compounds have sub-lethal toxicity at the 10 pM-100 nM range on multi-generation assays. We examined the acute lethal toxicity and multi-generational sublethal toxicity (fecundity and reproduction) of perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and salts of perfluoro-1-octansulfonic acid (PFOS) using 1.7% agar Nematode Growth Medium (NGM) plates. The fluorine compounds affected the fecundity of C. elegans at concentrations 10⁵- to 10⁸-fold lower than the median effective concentrations (EC₅₀). In particular, worm abundance during the first generation did not differ significantly from controls, while in contrast, the number of worms in the fourth generation at 10 pM PFOS-tetraethylammonium (TEA) decreased significantly to about 50% of control (p < 0.01) and the number of eggs and worms in the fourth generation at 1 nM PFNA decreased significantly to about 30% of control (p < 0.01). However, no dose-response relationship was observed in this study. We confirmed that perfluoro organic compounds strongly disrupt fecundity in C. elegans.

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Nematodes are highly abundant organisms found in soil or sedimentary habitats. The free-living nematode

Caenorhabditis

(C. elegans) has been used as an excellent model for monitoring ecotoxicity in soil. We have previously demonstrated that the lifespan of C. elegans can be used as an endpoint for detecting the ecotoxicity of heavy metals and detergents, and have developed a novel ecotoxicity assay based on their shortened lifespan. Herein we used a daf-16(mu86) mutant CF1038 strain, which has a deficient transcription factor DAF-16 regulating a variety of genes involved in longevity and stress response, for ecotoxicity assays. We carefully examined the effects on reproduction, larval growth, and lifespan in the short-lived CF1038 strain and wild-type N2 strain in the presence of a perfluoro organic compound (pentadecafluorooctanoic acid) and an organophosphate insecticide (dichlorvos) in addition to heavy metals (CuSO₄ and CdCl₂) and detergents (sodium dodecyl sulfate and a commercially available household detergent). Unexpectedly, both strains exhibited comparable reductions in these endpoints including lifespan by exposure to these ecotoxicants, indicating that DAF-16 does not largely contribute to tolerance to these agents. By virtue of a shorter assay period, the lifespan-based assay using the daf-16 mutant can be useful for assessing the ecotoxicity of a variety of ecotoxic chemicals.

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The free-living nematode,

Caenorhabditis

elegans

(C. elegans) was adopted as a multicellular biosensor of biological toxicity from alkylphenols and organotin compounds. Alkylphenols were found to affect reproduction at lower doses than indicated by the acute toxicity assay. In particular, nonylphenol altered the reproduction rate of C. elegans at a dose 10- to 100-fold lower than the 50% lethal concentration (LC₅₀). A comparison of the number of viable worms and eggs suggested that alkylphenols and organotin compounds possess hatching toxicity. A 0.1 μM dose of organotin compounds caused a significant decrease, in the order of 20-50%, in reproduction of the worms, and an abnormal male: hermaphrodite ratio was observed. C. elegans therefore appears to represent a potent and sensitive organism with which to evaluate the biological effects of chemicals. In particular, the sensitivity of reproduction as an endpoint is highly useful for assessing the sublethal effects of chemicals.

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線虫には約 150 種類の N 型糖鎖の存在が判明している。本稿では，無脊椎動物に多く存在し，脊椎動物にないパウチマンノース型 N-グリカンの合成と機能について考察する。線虫の糖鎖はフコシル化とホスフォリルコリン付加により，多様性を呈しており，ホスフォリルコリンは多くの病原菌において抗原決定基として知られている。パウチマンノース型 N-グリカンの合成には，UDP-GlcNAc:α3-D-マンノシド β1,2-N-アセチルグルコサミン転移酵素（GnTI, Mgat1 遺伝子によってコードされる）反応が先行する。線虫では，GnTI に 3 つのアイソザイム（GLY-12, GLY-13, GLY-14）がある。それぞれのアイソザイムは標的蛋白質が異なっており，線虫の病原菌に対する防御において異なった機能を持つ。線虫における GnTI 標的蛋白質の同定により，無脊椎動物及び脊椎動物の感染防御における GnTI 標的糖蛋白質の機能が明らかになるものと期待される。

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The time spent as a dauer larva does not affect adult life span in

Caenorhabditis

, as if aging is suspended in this quiescent developmental stage. We now report that modest doses X-irradiation of dauer larvae increased their post-dauer longevity. Post-irradiation incubation of young dauer larvae did not modify this beneficial effect of radiation. Conversely, holding dauer larvae prior to irradiation rendered them refractory to this X-radiation-induced response. We present a model to explain these results. These experiments demonstrate that dauer larvae provide an excellent opportunity to study mechanisms by which X irradiation can extend life span.

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The hormetic effect, which extends the lifespan by various stressors, has been confirmed in

Caenorhabditis

(C. elegans). We have previously reported that oxidative stress resistance in a long-lived mutant age-1 is associated with the hormesis. In the age-1 allele, which activates an insulin/insulin-like growth factor-1 (Ins/IGF-1) signaling pathway, the superoxide dismutase (SOD) and catalase activities increased during normal aging. We now demonstrate changes in the mitochondrial superoxide radical (·O₂^-) levels of the hormetic conditioned age-related strains. The ·O₂^- levels in age-1 strain significantly decreased after intermittent hyperoxia exposure. On the other hand, this phenomenon was not observed in a daf-16 null mutant. This hormesis-dependent reduction of the ·O₂^- levels was observed even if the mitochondrial Mn-SOD was experimentally reduced. Therefore, it is indicated that the hormesis is mediated by events that suppress the mitochondrial ·O₂^- production. Moreover, some SOD gene expressions in the hormetic conditioned age-1 mutant were induced over steady state mRNA levels. These data suggest that oxidative stress-inducible hormesis is associated with a reduction of the mitochondrial ·O₂^- production by activation of the antioxidant system via the Ins/IGF-1 signaling pathway.

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The molecular mechanism of aging, which has been a “black box” for many years, has been elucidated in recent years, and the nematode C. elegans, which is a model animal for aging research, has played a major role in its elucidation. From the analysis of C. ‍elegans longevity-related mutant genes, many signal trans­duction systems, with the insulin/insulin-like growth factor signal transduction system at the core, have emerged. It has become clear that this signal transduction system is greatly affected by external nutrients and is involved in the downstream regulation of oxidative stress, which is considered to be one of the main causes of aging.

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The nematode

Caenorhabditis

has proven a robust genetic model for studies of aging and the roles of oxidative stress. In this review we focus on the genetics of select long-lived and short-lived mutants of C. elegans that have proven useful in revealing the relationships that exist between oxidative stress and life span. The former are known to be controlled by an insulin/insulin-like growth factor (IGF-1)-like pathway, while the latter are affected by mitochondrial functions.

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Effects of a one-generation exposure to a natural estrogen, 17β-estradiol (E2), and environmental pollutants such as bisphenol A (BPA) and tributyltin chloride (TBTCL) on the number of germ cells were investigated in the hermaphrodite

Caenorhabditis

. The eggs of gravid adult worms isolated by alkaline hypochlorite treatment were seeded on a test chemical-containing NGM (nematode growth medium) agar plate without cholesterol. After incubation for 6 days at 16°C, the germ cells of adult worms were stained with 4', 6-diamino-2-phenylindole dihydrochloride (DAPI). The staining procedure was completed within one hour and the stained germ cells were counted under a fluorescence microscope without dissection. The number of germ cells in the worms treated with E2 (10^-10-10^-6 M) and BPA (10^-9-10 ^-5 M) was significantly increased. Maximal increases were observed at 10^-8 M E2 (156 ± 15.3% of control) and 10^-5 M BPA (168 ± 20.0 % of control). TBTCL (10^-9-10^-6 M) significantly decreased the number of germ cells. The minimal decrease was observed at 10^-6 M TBTCL (30.2 ± 3.51% of control). These results indicate that changes in the number of germ cells are a sensitive indicator of the effects of chemicals on the reproductive system. Since the method described in this paper is a novel, simple, time- and money-saving bioassay, C. elegans is an excellent model with which to determine the reproductive toxicity of chemicals including environmental pollutants.

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Resveratrol, a member of a class of polyphenolic compounds known as flavonols, has been extensively studied for its anticancer, antiviral, anti-inflammatory, and neuroprotective roles. Caenorhabidits elegans is a well-established animal for investigating responses to radiation. We found that resveratrol may provide protection against hazardous radiation. Pre-treatment with resveratrol extended both the maximum and mean life span of irradiated C. elegans. Resveratrol acted as a strong radical scavenger and regulated superoxide dismutase (SOD) expression. In addition, resveratrol was shown to be capable of alleviating γ-ray radiation exposure-induced reduction in mitochondrial SOD expression. Ultimately, a correlation may exist between dietary intake of trace amounts of resveratrol and anti-aging effects. A specific response mechanism may be activated after the administration of resveratrol in irradiated animals. Our results suggest the protective effect of resveratrol is due to its strong ability to protect from oxidative stress and protective effects in mitochondria. Therefore, resveratrol is potentially an effective protecting agent against irradiative damage.

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ミズキ科サンシュユの新鮮葉から精製エラジタンニン標品を得た. 線虫

Caenorhabditis

を同調培養した. 未成熟成虫と抱卵成虫をこのタンニン (10ppm濃度) に5日間暴露しても運動能に若干の低下が認められたものの, 未成熟成虫は死亡せず, 抱卵成虫の死亡率も7%に過ぎなかった. しかし, 未成熟成虫の性的成熟および抱卵成虫の繁殖能は阻害された. L1幼虫の運動能も低下しなかったが, その成長は阻害された. 同濃度下でさらに暴露試験を続けると, 抱卵成虫と未成熟成虫の死亡率は急激に高まり, 10日目で未成熟成虫の死亡率は56%, 抱卵成虫で78%に達した. しかし, L1幼虫は死亡しなかった. 1ppm濃度下でL1幼虫の成長が若干阻害された. 1000ppm濃度下でなお生存していた抱卵成虫の内臓は溶解・消失していた. しかし, 体内での卵割は認められた.

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Streptococcus thermophilus bacteria, which are widely used as fermented starter for dairy production, exert various beneficial health effects. Nevertheless, even though pro-longevity effects of various probiotics have been reported, no report has described Streptococcus thermophilus effects on longevity. This study was conducted to evaluate Streptococcus thermophilus effects on lifespan extension and to elucidate the Streptococcus thermophilus-mediated longevity mechanism using

worms as a model animal. They were fed standard food (Escherichia coli OP50) or Streptococcus thermophilus from the young adult stage. Feeding with Streptococcus thermophilus, compared to Escherichia coli OP50, to

Caenorhabditis

extend the lifespan, reduced lipofuscin accumulation, and maintain vigorous locomotion. Feeding with Streptococcus thermophilus did not alter the worm growth curve or the offspring number, indicating that the Streptococcus thermophilus-mediated lifespan extension is not attributable to caloric restriction. The qRT-PCR data showed that Streptococcus thermophilus increased the expression of daf-16 and some of its downstream antioxidant genes. Furthermore, the pro-longevity effects of Streptococcus thermophilus were decreased in loss-of-function mutant of daf-16. Results show that Streptococcus thermophilus extends the lifespan of

Caenorhabditis

through DAF-16-mediated antioxidant pathway activation.

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腸内細菌やプロバイオティクスによる疾患や健康の制御に向けたアプローチが盛んに試みられる一方，腸内細菌と宿主間の相互作用の分子的実体には未解明な点も多い．線虫

（C. elegans）は，3つのノーベル賞研究をはじめとして，さまざまな生命現象の発見において重要な役割を果たしてきたモデル生物の一つであるが，腸内細菌研究においても例外ではない．乳酸桿菌やビフィズス菌による線虫の寿命延伸作用が報告されて以降，哺乳動物実験の削減・廃止の動きも相まって，線虫を代替モデルとしたプロバイオティクスや有用菌の生体作用に関する知見が急速に蓄積している．線虫固有の腸内細菌叢についての理解も進むなか，腸内細菌叢―宿主間相互作用の解明に向けて線虫モデルの活用がますます期待される．

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