Organogenic Period Research Articles

Teratogenicity of tellurium dioxide: prenatal assessment.

The effects of multiple maternal subcutaneous injections of tellurium dioxide (TeO2) suspended in olive oil (0-1,000 mumol/kg) from day 15 to day 19 of gestation were evaluated in the Wistar rat. External and internal soft-tissue examinations were performed on day 20 fetuses. Multiple maternal injections, at doses higher than 10 mumol/kg, resulted in a dose-related appearance of hydrocephalus, edema, exophthalmia, ocular hemorrhage, umbilical hernia, undescended testis, and small kidneys in fetuses on day 20 of gestation. At 500 mumol/kg, reduction in maternal weight gain was also observed. At this level, the incidence of the above anomalies was 100%. The 100 mumol/kg dose of Te, which did not produce apparent maternal toxic responses, resulted in a 100% incidence of hydrocephalus and edema but no fetal mortality. Thus, tellurium can be teratogenic to the rat fetus without concomitant maternal toxicity. Also, the fetal period may be more sensitive than the organogenic period for the induction of hydrocephalus. Such evidence is consistent with the development of the choroid plexus and an effect of TeO2 on the production/resorption of cerebrospinal fluid.

Some teratogenic properties of ethanol and acetaldehyde in C57BL/6J mice: implications for the study of the fetal alcohol syndrome.

To investigate the teratogenic effect of acute alcohol exposure, pregnant C57BL/6J mice were exposed to 25% ethanol (either two doses of 2.9g/kg or one dose 5.8g/kg) during the organogenic period either by intraperitoneal injections or by intubation. The incidence of malformations varied according to (1) the stage of embryonic development at the time of exposure, (2) the route of administration of the alcohol, and (3) the amount of alcohol given and the time period over which it was administered. Oral doses of alcohol were teratogenic although less so than the same dose given intraperitoneally, and two intraperitoneal doses four hours apart produced significantly more malformation than the same two doses six hours apart. The primary metabolite of alcohol, acetaldehyde, was also investigated for its teratogenicity. It was found that one or two doses of four percent acetaldehyde (0.32g/kg), administered intraperitoneally were teratogenic. A further attempt was made to raise blood acetaldehyde levels by exposing mice to disulfiram, an inhibitor of acetaldehyde dehydrogenase, prior to administration of alcohol. The disulfiram pretreatment did not increase the malformation rate. Treatment with alcohol on day 7 or 8 caused a variety of facial abnormalities, some of which were comparable to those seen in children with fetal alcohol syndrome. Exposure on day 9 or 10 resulted in limb defects. The results suggest that one or more episodes of heavy maternal drinking at critical periods in pregnancy may severely damage the embryo and may produce many features of the fetal alcohol syndrome.

Comparative Study of the Rates of Organogenesis of Normal and Cecidial Shoots in Shorea curtisii Dyer ex King (Dipterocarpaceae)

In the neoformational epiphyllous bud-gall of Gallacoccus anthonyae Beardsley (Eriococcidae), the growth of the cecidial shoot occurs in two developing periods induced by the insect. These two organogenic periods are separated by a resting period which corresponds to the molting and moving stage of the insect. During each of the developing periods, 12 leaves are formed in distichous arrangement. The leaves appear at 6-day intervals. At the end of the second organogenic period, the gall-apex becomes parenchymatous. In the bud-gall of Gallacoccus secundus Beardsley, the development of the cecidial shoot occurs in only one organogenic period. The neoformational apex produces 3 leaves in distichous arrangement and then aborts. The interval between two leaf initiations is less than 10 days. As regards the rate of organogenesis (one leaf every 6 days) and the fate (degeneration) of the apex, the cecidial buds and the terminal bud of the seedling, which is stimulated into hyperactivity after transplantation, are comparable. However, the distichous arrangement in the cecidial buds and the existence in the gall of G. anthonyae of two successive developing periods recall the behavior of the plagiotropic normal buds of Shorea curtisii.

Developmental precocity in transferred mouse embryos influencing the teratogen response to salicylate

Asynchronous blastocyst transfer, supposed to equalize the developmental stage of native and alien embryos during the organogenic period, was used as a tool in a teratological investigation. A spurious protection by the transfer as such was shown to depend on a persisting asynchrony between native and alien foetuses. The initial difference of 24 h was not nullified, but decreased to 8 h. This difference allowed transferred foetuses to pass the period of maximum sensitivity before salicylate treatment.