Yahoo奇摩 網頁搜尋

  1. 約 43,500,000 項搜尋結果

  1. Nitrite oxidoreductase (NOR or NXR) is an enzyme involved in nitrification.It is the last step in the process of aerobic ammonia oxidation, which is carried out by two groups of nitrifying bacteria: ammonia oxidizers such as Nitrosospira, Nitrosomonas and Nitrosococcus convert ammonia to nitrite, while nitrite oxidizers such as Nitrobacter and Nitrospira oxidize nitrite to nitrate.

  2. › wiki › ChloroformChloroform - Wikipedia

    Chloroform, or trichloromethane, is an organic compound with formula C H Cl 3 and is a common organic solvent.It is a colorless, strong-smelling, dense liquid that is produced on a large scale as a precursor to PTFE.It is also a precursor to various refrigerants. [8] It ...

    • CHCl₃
    • 119.37 g·mol−1
    • −63.5 °C (−82.3 °F; 209.7 K)
    • 10.62 g/L (0 °C), 8.09 g/L (20 °C), 7.32 g/L (60 °C)
    • Classification of Co-Carcinogen
    • Common co-carcinogens
    • Issues

    The International Agency for Research on Cancer (IARC), established in 1965 as a subunit of World Health Organization, classify carcinogens into four groups.Co-carcinogen is not in any of these four groups. 1. Group 1: Carcinogenic to humans. 2. Group 2A: Probably carcinogenic to humans. 3. Group 2B: Possibly carcinogenic to humans. 4. Group 3: Not...

    Co-carcinogens can be a lifestyle like cigarette-smoking, alcohol-drinking or even areca nut tobacco-chewing, which is an Asian tradition, because those activities promote the cytopathic effect (CPE). Also, some virus are co-carcinogens like Herpesviruses, Epstein–Barr virus (EBV) and human herpesvirus 4 (HHV-4) Over intake beta carotene for a long...

    Experiments for human toxicology require a long term following and a large amount of investment in order to classify a chemical as co-carcinogens, carcinogens or anti-carcinogenic. In recent years, people substitutes health supplement for healthy meal.[citation needed] Some myths even state beta carotene[failed verification] as elixir in developing...

  3. › wiki › GenotoxicityGenotoxicity - Wikipedia

    • Mechanism
    • Test Techniques
    • in Vitro Toxicology Testing
    • Cancer
    • See Also

    The genotoxic substances induce damage to the genetic material in the cells through interactions with the DNA sequence and structure. For example, the transition metal chromium interacts with DNA in its high-valent oxidation state so to incur DNA lesions leading to carcinogenesis. The metastable oxidation state Cr(V) is achieved through reductive a...

    The purpose of genotoxicity testing is to determine if a substrate will influence genetic material or may cause cancer. They can be performed in bacterial, yeast, and mammalian cells.With the knowledge from the tests, one can control early development of vulnerable organisms to genotoxic substances.

    The purpose of in vitro testing is to determine whether a substrate, product, or environmental factor induces genetic damage. One technique entails cytogenetic assays using different mammalian cells. The types of aberrations detected in cells affected by a genotoxic substance are chromatid and chromosome gaps, chromosome breaks, chromatid deletions...

    Genotoxic effects such as deletions, breaks and/or rearrangements can lead to cancer if the damage does not immediately lead to cell death. Regions sensitive to breakage, called fragile sites, may result from genotoxic agents (such as pesticides). Some chemicals have the ability to induce fragile sites in regions of the chromosome where oncogenes a...

  4. › wiki › CarcinogenCarcinogen - Wikipedia

    • Radiation
    • in Prepared Food
    • in Cigarettes
    • Mechanisms of Carcinogenicity
    • Classification
    • Common Carcinogens
    • Major Carcinogens Implicated in The Four Most Common Cancers Worldwide
    • External Links

    CERCLA identifies all radionuclides as carcinogens, although the nature of the emitted radiation (alpha, beta, gamma, or neutron and the radioactive strength), its consequent capacity to cause ionization in tissues, and the magnitude of radiation exposure, determine the potential hazard. Carcinogenicity of radiation depends on the type of radiation...

    Chemicals used in processed and cured meat such as some brands of bacon, sausages and ham may produce carcinogens. For example, nitrites used as food preservatives in cured meat such as bacon have also been noted as being carcinogenic with demographic links, but not causation, to colon cancer. Cooking food at high temperatures, for example grilling...

    There is a strong association of smoking with lung cancer; the risk of developing lung cancer increases significantly in smokers. A large number of known carcinogens are found in cigarette smoke. Potent carcinogens found in cigarette smoke include polycyclic aromatic hydrocarbons (PAH, such as benzo(a)pyrene), benzene, and nitrosamine.

    Carcinogens can be classified as genotoxic or nongenotoxic. Genotoxins cause irreversible genetic damage or mutations by binding to DNA. Genotoxins include chemical agents like N-nitroso-N-methylurea (NMU) or non-chemical agents such as ultraviolet light and ionizing radiation. Certain viruses can also act as carcinogens by interacting with DNA. No...

    International Agency for Research on Cancer

    The International Agency for Research on Cancer (IARC) is an intergovernmental agency established in 1965, which forms part of the World Health Organization of the United Nations. It is based in Lyon, France. Since 1971 it has published a series of Monographs on the Evaluation of Carcinogenic Risks to Humansthat have been highly influential in the classification of possible carcinogens. 1. Group 1: the agent (mixture) is definitely carcinogenic to humans. The exposure circumstance entails exp...

    Globally Harmonized System

    The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is a United Nationsinitiative to attempt to harmonize the different systems of assessing chemical risk which currently exist (as of March 2009) around the world. It classifies carcinogens into two categories, of which the first may be divided again into subcategories if so desired by the competent regulatory authority: 1. Category 1: known or presumed to have carcinogenic potential for humans 1.1. Category 1A: t...

    U.S. National Toxicology Program

    The National Toxicology Program of the U.S. Department of Health and Human Services is mandated to produce a biennial Report on Carcinogens. As of June 2011, the latest edition was the 12th report (2011).It classifies carcinogens into two groups: 1. Known to be a human carcinogen 2. Reasonably anticipated being a human carcinogen

    Occupational carcinogens

    Occupational carcinogens are agents that pose a risk of cancer in several specific work-locations:


    1. Gasoline(contains aromatics) 2. Leadand its compounds 3. Alkylating antineoplastic agents (e.g. mechlorethamine) 4. Styrene 5. Other alkylating agents (e.g. dimethyl sulfate) 6. Ultraviolet radiationfrom the sun and UV lamps 7. Alcohol(causing head and neck cancers) 8. Other ionizing radiation(X-rays, gamma rays, etc.)

    In this section, the carcinogens implicated as the main causative agents of the four most common cancers worldwide are briefly described. These four cancers are lung, breast, colon, and stomach cancers. Together they account for about 41% of worldwide cancer incidence and 42% of cancer deaths (for more detailed information on the carcinogens implic...

  5. Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abnormal cell division. Cell division is a physiological process that occurs in almost all tissues and under a ...

  6. Carcinogenic parasite. Carcinogenic parasites are parasitic organisms that depend on other organisms (called hosts) for their survival, and cause cancer in such hosts. Three species of flukes ( trematodes) are medically-proven carcinogenic parasites, namely the urinary blood fluke ( Schistosoma haematobium ), the Southeast Asian liver fluke ...

  1. 其他人也搜尋了