| It showed in the survey of neonate birth in 1987 that about three hundred thousands up to four hundred thousands deficient infants were bora in our country every year. The incidence of them was 13.07‰, and there were 101 types of birth defects. Moreover about forty percent of neonate death during the birth was attributed to birth defects. It was demonstrated that about ten percent of birth defects were induced by environmental factors, while about sixty-five up to seventy percent of them were jointly induced by genetic factors and environmental factors. Therefore, it is very crucial for effectively preventing birth defects to screen teratogens and elaborate the mechanism of chemical teratogenicity. With the development of new technologies such as combinational chemical, computer-aided drug design, rational drug discovery and metabolic engineering, the number of new chemicals increase dramatically. Thus it is essential to use rapid and high throughput methods for screening lead chemicals. However, the current teratogenic assays can not satisfy with an increasing need to the risk assessment and the mechanistic research of chemical teratogenicity.During the past two decades many different in vivo and in vitro assays have been established. With the application of new biotechnologies to toxicology, now the testing assays of teratogens are developmenting towards the alternation to in vivo assays and in vitro high throughput methods in order to rapidly screen new chemicals and reduce the number of experimental animals used. To date more than 30 different culture systems have been proposed as in vitro alternatives to existing in vivo assays for developmental toxicity. According to the culture system they include cell culture assays using either primary cell cultures or immortalized cell lines. At a higher integration level the development of organ anlagen been employed in assays for developmental toxicity. The most complex assays in thisarea make use of isolated postimplantation mammalian embryos which are cultured in vitro during the phase of major organogenesis. The primary cell cultures such as rat midbrain neural cells and moue limb bud cells have most disadvantage with requiring animal material as well as the difficulty of standardization. The most promising immortalized murine embryonic stem cell tests need future validations, with the disadvantage of the technical difficulty and being expensive. Likewise the tissue or organ cultures and whole embryo cultures have a unique value in the mechanistic research of chemical developmental toxicity, with the disadvantage of the use of experimental animal, the technical difficulty and being laborious.This present study was aimed at designing and evaluating an in vitro inexpensive and easy-to-perform screening assay of potential teratogens. In some details, the cell proliferation and morphology of cultured mouse fibroblastoid L929 cells were determined ,employing computer-aided video recording, followed by detection of the stained specimen and calculation of endpoint values by the use of a computerized microscope workstation. Three different parameters were combined empirically into a single index describing general alterations in cell morphology, and, subsequently, measurements of alterations in cell morphology and proliferation were combined to produce a single empirical index (teratogenicity index,TI) aimed at predicting teratogenic potency. 8 compounds were tested by this assay, 5 of which that demonstrated in vivo teratogenic potentials: retinoic acid (RA), methotrexate (MTX), 5-bromo-2'-deoxyuridine(BrdU), 5-fluorouracil(5-FU) and mitomycin C(MC) and 3 of which that demonstrated in vivo nonteratogenic potentials: ascorbic acid(VC), penicillin G(PenG) and saccharin. Firstly, two teratogens(RA , MTX) and two non-teratogens(VC, PenG) were used to demonstrate the relation between chemical teratogenic potency and the alterations of cell proliferation and cell morphology. The result suggested the nonteratogens generally caused smaller alterations in cell proliferation and cell morphology than the teratogens. The data support that the TI value was relative to the chemical teratogenic potency with a linear dose-response relationship and may be employed for in vitro screenings for potential teratogens. Then the predictive value of TI is 5... |
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