[Standardized treatment of chronic radiation-induced bowel injury].

Radiation-induced bowel injury is a common complication of radiation therapy for pelvic malignancy. Given the huge number of patients diagnosed with pelvic malignancy, the number of patients diagnosed with radiation-induced bowel injury increased year by year, which put a great burden on the clinical diagnosis and treatment of radiation-induced bowel injury. In particular, chronic radiation-induced bowel injury, which is manifested in the process of prolonged, repeated and progressive aggravation, seriously affects the physical and mental health of patients and makes clinical diagnosis and treatment difficult. However, due to insufficient attention and understanding from doctors and patients, standardized diagnosis and treatment of radiation-induced bowel injury still have a long way to go. Radiation-induced bowel injury is self-limited but irreversible. During diagnosis, we should pay attention to overall evaluation of the stage of disease based on clinical symptoms, endoscopic examination, imaging examination, pathology and nutritional risk. The treatment methods include health education, drug therapy, enema therapy, formalin local treatment, endoscopic treatment and surgical treatment, etc. The treatment decision-making should be based on clinical symptoms, endoscopic or imaging findings to alleviate the clinical symptoms of patients as the primary goal and to improve the long-term quality of life of patients as the ultimate goal.

Micronucleus assays with Tradescantia pollen tetrads: an update.

Micronucleus (MN) assays with early pollen tetrad cells of Tradescantia (Trad-MN assays) are at present the most widely used bioassays with plants for the detection of genotoxins in the environment. So far, ∼ 160 chemicals have been tested and ∼ 100 articles that concern complex environmental mixtures were published. This article summarises the results of Trad-MN studies, which have been carried out during the last 15 years with individual compounds and investigations concerning the pollution of environmental compartments (soil, water and air). The evaluation shows that the effects of certain genotoxins such as heavy metals, radionuclides, pesticides and air pollutants can be easily detected with this test. Comparisons with results obtained in MN studies with mitotic (root tip) cells indicate that meiotic tetrad cells are in general more sensitive. Important issues for future research concern the evaluation of the suitability of wildlife Tradescantia species that are sometimes used instead of specific clones (such as #4430 for which standardised protocols have been developed) as well as the assessment of the predictive value of Trad-MN results in regard to the prediction of cancer hazards in humans and adverse effects at the ecosystem level. The fact that the genotoxic effects of certain compound such as metals, which can be detected with plant bioassays, in particular with the Trad-MN assay but not in other commonly used bioassays (e.g. in bacterial tests) makes them an essential element in the batteries for environmental monitoring.

Antimutagenic property of an herbal medicine, Polygonum multiftorum Thunb. detected by the Tradescantia micronucleus assay.

The root extracts of a Chinese herb, Polygonum multiflorum Thunb., have been used for centuries as an internal medicine to improve liver and kidney functions. In this study, we evaluated the antimutagenic property of this drug with the Tradescantia micronucleus (Trad-MCN) assay. The Trad-MCN bioassay is a well-established test for chromosome damage induced by physical or chemical agents in terms of micronuclei (MCN) frequency. Inflorescences of the Tradescantia plant cuttings were first exposed to 0.35 Gy soft X-rays (80 kV, 5 mA, 1 mm Al filter, dose rate around 0.50 Gy/min), followed by drug treatments at 1, 3, and 6% concentrations of the aqueous solution for a total recovery period of 24 hours. The positive (X-rays), negative (nutrient solution), and drug control (3% drug solution) groups were maintained in each of the three series of repeated experiments. Flower buds of the treated and control groups were fixed in aceto-alcohol (1:3 ratio) in preparation for slides to score MCN frequencies in the early tetrads of the meiotic pollen mother cells. The mean MCN frequencies (MCN/100 tetrads +/- SE) of the positive control (irradiated) was 26.68 +/- 2.49; the negative control was 2.93 +/- 0.50; the PM solution control was 2.06 +/- 0.39, and the 0.35 Gy X-ray plus 6% PM drug treated was 18.76 +/- 1.69. A 45% reduction in chromosome damage was observed. Antimutagenic effects were relatively decreased at lower concentrations of PM. This antimutagenic effect could be attributed to the antioxidant action of PM, enhancement of DNA repair, or the radical elimination from the irradiated plant cells.

The improved Allium/Vicia root tip micronucleus assay for clastogenicity of environmental pollutants.

The meristematic mitotic cells of plant roots are appropriate and efficient cytogenetic materials for the detection of clastogenicity of environmental pollutants, especially for in situ monitoring of water contaminants. Among several cytological endpoints in these fast dividing cells, such as chromosome/chromatid aberrations, sister-chromatid exchanges and micronuclei, the most effective and simplest indicator of cytological damage is micronucleus formation. Although the Allium cepa and Vicia faba root meristem micronucleus assays (Allium/Vicia root MCN) have been used in clastogenicity studies about 12 times by various authors in the last 25 years, there is no report on the comparison of the efficiency of these two plant systems and in different cell populations (meristem and F1) of the root tip as well as under adequate recovery duration. In order to maximize the efficiency of these bioassays, the current study was designed to compare the Allium and the Vicia root MCN assays on the basis of chromosome length, peak sensitivity of the mitotic cells, and the regions of the root tip where the MCN are formed. The total length of the 2n complement of Allium chromosomes is 14.4 microns and the total length of the 2n complement of Vicia is 9.32 microns. The peak sensitivity determined by serial fixation at 12-h intervals after 100 R of X-irradiation is 44 h. The slope of the X-ray dose-response curve of Allium roots derived from the meristematic regions was lower than that derived from cells in the F1 region. Higher efficiency was also demonstrated when the MCN frequencies were scored from the F1 cells in both Allium and Vicia treated with formaldehyde (FA), mitomycin C (MMC), and maleic hydrazide (MH). The results indicated that scoring of MCN frequencies from the F1 cell region of the root tip was more efficient than scoring from the meristematic region. The X-ray linear regression dose-response curves were established in both Allium and Vicia cell systems and the coefficients of correlations, slope values were used to verify the reliability and efficiency of these two plant cell systems. Based on the dose-response slope value of 0.894 for Allium and 0.643 for Vicia, the Allium root MCN was a more efficient test system. The greater sensitivity of the Allium roots is probably due to the greater total length of the diploid complement and the higher number of metacentric chromosomes.(ABSTRACT TRUNCATED AT 400 WORDS)

Genotoxic effects of the chlorinated hydroxyfuranones 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone and 3,4-dichloro-5-hydroxy-2[5H]-furanone in Tradescantia micronucleus assays.

This is the first report of clastogenic effects of chlorinated hydroxyfuranones (CHFs) in plants. Two byproducts of water chlorination, 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX) and 3,4-dichloro-5-hydroxy-2[5H]-furanone (MA) induced a dose dependent increase of micronuclei (MN) in pollen mother cells of Tradescantia when doses up to 100 micrograms MX and 500 micrograms MA were applied directly to the inflorescences. In contrast, exposure of the stems in aqueous solutions containing up to 1 mg/l MX and 10 mg/l MA did not cause a positive response.

Vicia cytogenetic tests for environmental mutagens. A report of the U.S. Environmental Protection Agency Gene-Tox Program.

Vicia root-tip mitotic and pollen mother-cell meiotic tests are two major kinds of cytogenetic tests for environmental mutagens. According to the present review, 81 of 85 earlier studies used mitotic tests to determine the frequencies of chromosome or chromatid aberrations and/or sister-chromatid exchange from root-tip meristematic cells; only 4 used meiotic tests to determine the frequencies of chromosome aberration from pollen mother cells. Treatment of root-tip meristem can be done by allowing the newly germinated roots to absorb the chemical mutagens from a water solution. Pollen mother cells can be treated by spraying the solution or pipetting the liquid over the flower buds. After an appropriate recovery time, the samples are fixed and stained, and the slides are prepared for metaphase or anaphase figures for scoring aberration frequencies. Slides for meiotic tests are prepared for metaphase I and/or Anaphase I stages for scoring chromosome aberration frequencies. Results of both cytogenetic tests should be expressed in terms of number of breaks per cell or per 100 cells. Test results of 76 chemicals from 32 classes in this review indicate that the Vicia root-tip mitotic test is reliable, efficient, and relatively inexpensive. These results also reveal that antibiotics are most frequently studied, followed by alkyl sulfones, pyrimidine, and purine derivatives. Of all the agents studied through root-tip mitotic tests, about 90% gave positive responses; antibiotics (phleomycin and bleomycin) had very high mutagenicity (less than 1 ppm gave positive response).

Tradescantia micronucleus bioassay and pollen tube chromatid aberration test for in situ monitoring and mutagen screening.

The meiotic pollen mother cells (PMC) of Tradescantia (spiderwort) are highly synchronized in their prophase I and tetrad stages. Chromosomes of this stage are sensitive to physical or chemical mutagens. Thus high frequency of acentric fragments or sticky chromosomes can be induced with very low level of mutagens. These induced chromosome aberrations become micronuclei (MCN) in the synchronized tetrads and they can be easily identified and scored. Based upon these features, the Tradescantia micronucleus bioassay was established. This bioassay involves the exposure of PMC in the young inflorescences of the plant cuttings to gaseous agents through diffusion, to liquid agent through absorption and dialysis from the stem to flower buds, or to radiation. The exposed samples are fixed in aceto-alcohol (1:3) and prepared into microslides by using the aceto-carmine squash method. Frequencies of MCN in a large population of synchronized tetrads are the indications of genetic damage caused by the agents. Mature pollen grains of Tradescantia are free cells which can be cultured in lactose-agar medium. The generative cells in the cultured pollen tubes can carry out mitosis similar to the in vivo condition. The G2 interphase chromosomes of pollen mitosis are highly sensitive to gaseous or liquid chemicals and radiation. Treatments can be applied to these mitotic generative cells of the mature pollen or the mitotic generative nuclei of the developing pollen tube. The mitotic chromosomes of the generative cells are allowed to proceed through mitosis in the culture medium and slides are prepared for metaphase figures. Frequencies of various types of chromatid aberrations can be scored and used as the indices of genetic damage.