1,721,758 research outputs found
The chick embryo cytogenetic test: experience with agrochemicals and phthalates
No full textAlthough chick embryos have been used widely as model systems for studies in experimental embryology and teratology, it is only in the '70s that Bloom and co-workers (1) developed a chick embryo cytogenetic test (CECT) to detect the genetic damage resulting from exposure to radiation and chemicals. Early in chick development when no definite liver is present, mixed-function oxidase activity is expressed and various types of mutagen-carcinogens are activated to genotoxic forms. In this lab the CECT has been adapted for studying the genetic activity of xenobiotics of environmental relevance: genotoxicity is determined using SCE or chromosome aberration end point and cytotoxicity is assessed using cell cycle kinetics and mitotic index endpoints. Treatment is usually performed before incubation and metaphases are harvested at different times of development. It is possible to perform treatments externally to reproduce a major route of contamination in the wild, or by injection into the air cell so to dose embryos accurately.
With the CECT, three pesticides have been evaluated: maneb, a fungicide, and two phenoxy herbicides (MCPA and 2.4-D) and more recently the plasticizer DEHP. These studies along with the work of Bloom shows that this in vivo test system has good potentialities for evaluating the genotoxic risk posed to avian species by xenobiotics.
1 Bloom, S.E. & Hsu , T.C. Chromosoma 51: 261-267 (1975
Sister chromatid exchange induction by the herbicide 2,4-dichlorophenoxyacetic acid in chick embryos
No full textAs genetic damage may result from exposure to agricultural chemicals, it seemed appropriate to assess the genotoxic potential of 2,4-dichlorophenoxyacetic acid (2,4-D), a widely used broad-leaf herbicide, using a test system that may provide some indications on the genetic risk to animal species in the wild. In the present study, sister chromatid exchange (SCE) induction and cell cycle kinetics alterations by 2,4-D in 4-day old chick embryos were evaluated. Both a commercial herbicide formulation containing 37% 2,4-D isooctyl ester as active ingredient and pure 2,4-D were tested. Chick embryos were treated with 0, 0.5, 1, 2, or 4mg 2,4-D. Test solutions were applied to the inner shell membrane on day 0 of incubation. Either commercial formulation or pure 2,4-D induced a dose-related increase in SCE frequency over the concentration range from 0 to 4mg/embryo. Significantly higher SCE frequency was seen for the 4-mg group of embryos treated with the commercial product. A slightly higher SCE value was observed for the vehicle group (acetone-treated embryos) compared with the negative controls (untreated embryos). Significant inhibition of cell cycle progression was evident in both experimental groups and was generally dose related. The extent of changes in cell kinetics was similar in both groups, although somewhat more marked in the group treated with pure 2,4-D. The present findings corroborate the positive results from recent in vivo rodent studies
GENOTOXICIDAD DEL HERBICIDA ACIDO 2,4-DICLOROFENOXIACETICO.INDUCCION DE MICRONUCLEOS EN EMBRIONES DE POLLO
No full textLa prolongada exposición de especies animales a los agroquímicos podría conllevar un
riesgo de daños genéticos. En este estudio, se ha evaluado el potencial genotóxico de una
formulación comercial del herbicida ácido 2,4-diclorofenoxiacético (2,4-D - éster isooctílico -, 37% p/v como principio activo) ya que en el campo se emplean sustancias de grado técnico
y, además, con elevado porcentaje de ingredientes “inertes”. Son estas formulaciones las
que realmente pueden afectar a los ecosistemas locales. Los efectos genotóxicos del 2,4-D
se valoraron con la prueba del micronúcleo (MN) en el embrión de pollo - un sistema
experimental alternativo que puede proporcionar fiables indicaciones sobre el riesgo
genético de agentes de relevancia ambiental. El tratamiento fue efectuado antes de la incubación inyectando el 2,4-D en cámara de aire. Frotis de sangre periférica fueron preparados a 4, 7 y 10 días de incubación (D.I.). A 4 D.I., se observó inducción (P < 0.05)
de MN en embriones tratados con 4 mg del herbicida. Al prolongar el tiempo de exposición
(7-10 D.I.), se manifestaron claros efectos a dosis de 1 a 4 mg. La dosis de 0.5 mg fue inefectiva tanto a largo como a breve periodo de tratamiento. Esta acentuación de la
respuesta al 2,4-D podría ser el resultado de la persistencia de lesiones tempranas a las
cuales se añaden nuevas lesiones a medida que se alarga el tiempo de exposición
DNA synthesis and apoptosis in primary hepatocyte cultures from chick embryos after treatment with the herbicide 2,4-D
No full textChlorophenoxy herbicides belong to the peroxisome proliferator (PP) class of non-genotoxic hepatocarcinogens. The ability to stimulate DNA synthesis coupled with
the ability to suppress or delay apoptosis may play a role in PP carcinogenesis. There are no conclusive data on the carcinogenicity of phenoxy herbicides. 2,4-
dichlorophenoxyacetic acid (2,4-D) is an herbicide widely used in agriculture, forestry, and also in recreational areas. The widespread pattern of 2,4-D use may,
therefore, pose a threat to avian organisms as well to other wild species. Primary hepatocyte cultures of chick embryos were used to assess the effects of 2,4-D on
S-phase and apoptosis. Considering that PP tumorigenesis is species restricted, the PP Wy-14,643, a rodent hepatocarcinogen, was also tested. Both 2,4-D and
Wy-14,643 at a dose level of 100 M induced a slight positive effect on DNA synthesis, as detected after BrdU incorporation, and reduced the number of apoptotic
cells. These data support some experimental evidence that 2,4-D may act as a weak tumor promoter, although further experimentation is needed to confirm the
results of the present study
The chick embryo cytogenetic test: experience with agrochemicals and phtalates
No full textAlthough chick embryos have been used widely as model systems for studies in experimental embryology and teratology, it is only in the '70s that Bloom and co-workers (1) developed a chick embryo cytogenetic test (CECT) to detect the genetic damage resulting from exposure to radiation and chemicals. Early in chick development when no definite liver is present, mixed-function oxidase activity is expressed and various types of mutagen-carcinogens are activated to genotoxic forms. In this lab the CECT has been adapted for studying the genetic activity of xenobiotics of environmental relevance: genotoxicity is determined using SCE or chromosome aberration endpoint and cytotoxicity is assessed using cell cycle kinetics and mitotic index endpoints. Treatment is usually performed before incubation and metaphases are harvested at different times of development. It is possible to perform treatments externally to reproduce a major route of contamination in the wild, or by injection into the air cell so to dose embryos accurately.
With the CECT, three pesticides have been evaluated: maneb, a fungicide, and two phenoxy herbicides (MCPA and 2.4-D) and more recently the plasticizer DEHP. These studies along with the work of Bloom shows that this in vivo test system has good potentialities for evaluating the genotoxic risk posed to avian species by xenobiotics.
1 Bloom, S.E. & Hsu , T.C. Chromosoma 51: 261-267 (1975
S-phase, apoptosis and peroxisome proliferation in avian hepatocyte cultures following exposure to the phenoxy herbicide 2,4-D
No full textPhenoxyherbicides induce peroxisome proliferation, as do other structurally
related or unrelated chemicals which were found to be nongenotoxic carcinogens
in rodents. The widespread use of 2,4-dichlorophenoxyacetic acid (2,4-D) raised
concerns over the potential to produce cancer, yet results from epidemiological
and experimental studies do not provide definitive evidence that 2,4-D is
carcinogenic. The objective of the present study was to verify whether 2,4-D
might interfere with cell growth similar to other peroxisome proliferators using
cultured avian hepatocytes. Primary hepatocyte cultures from 18-day-old chick
embryos were exposed to 2,4-D for up to 72 h followed by an assessment of
replicative DNA synthesis and apoptosis. Further, peroxisome proliferation was
evaluated. Results showed that 2,4-D stimulated DNA synthesis and suppressed
spontaneous apoptosis, while the effects on peroxisome proliferation were less
evident
EL DI(ETILHEXIL)FTALATO (DEHP) INTERFIERE CON EL BALANCE MITOSIS/APOPTOSIS EN CULTIVOS DE HEPATOCITOS DE EMBRIÓN DE POLLO
No full textEl DEHP es empleado en la industria como plastificante, especialmente en la fabricación de productos de vinilo, y a no hacer parte de la matriz polimérica acaba desprendiéndose. Su amplio empleo puede contaminar el medio ambiente y por ende afectar a distintos ecosistemas. El DEHP hace parte de un amplio y diversificado grupo de xenobióticos denominado proliferadores de peroxisomas (PPs). Los PPs en especies responsivas no ejercen actividad genética, pero terminan induciendo carcinomas hepatocelulares. Entre las múltiples hipótesis sobre la mecánica del desarrollo de estos tumores, parece significativa la alteración de la homeostasis tisular del parénquima hepático que favorece el crecimiento de focos preneoplásticos. Considerando la relevancia ambiental del DEHP, pareció oportuno evaluar los efectos del DEHP sobre síntesis replicativa del ADN y apoptosis en cultivos primarios de hepatocitos de embrión de pollo. Actualmente existen solo estudios en mamíferos. Se evaluó perturbación del crecimiento en hepatocitos expuestos a DEHP (25, 50, 75 y 100 μM) a 48, 72, 96 y 120 hrs. Se observó inducción significativa (p <0.01) de la fase-S en los hepatocitos tratados con 100 μM a 72 hrs, mientras que el efecto fue menos evidente (p < 0.05) con 50 y 75 μM. A medida que aumenta el tiempo de cultivo los efectos se atenúan también en el grupo tratado con 100 μM. El DEHP suprimió la apoptosis en hepatocitos tratados con 75 y 100 μM (p < 0.05) a 72 hrs. La dosis de 25 μM no manifestó efectos en todos los momentos de cultivo evaluados. Siendo blanco principal de los PPs el hepatocito, este sistema experimental se demuestra como una herramienta útil para evaluar los riesgos de la exposición en el entorno natural a xenobióticos no genotóxicos y podría ser valorado como predictivo en particular para las aves
- …
