In utero exposure to microwave radiation and rat brain development

Timed-pregnancy rats were exposed in a circular waveguide system starting on day 2 of gestation. The system operated at 2,450 MHz (pulsed waves; 8 microseconds PW; 830 pps). Specific absorption rate (SAR) was maintained at 0.4 W/kg by increasing the input power as the animals grew in size. On day 18 of gestation the dams were removed from the waveguide cages and euthanized; the fetuses were removed and weighed. Fetal brains were excised and weighed, and brain RNA, DNA and protein were determined. Values for measured parameters of the radiated fetuses did not differ significantly from those of sham-exposed fetuses. A regression of brain weight on body weight showed no micrencephalous fetuses in the radiation group when using as a criterion a regression line based on two standard errors of the estimate of the sham-exposed group. In addition, metrics derived from brain DNA (ie, cell number and cell size) showed no significant differences when radiation was compared to sham exposure. We conclude that 2,450-MHz microwave radiation, at an SAR of 0.4 W/kg, did not produce significant alterations in brain organogenesis.     

Influence of nicotine and caffeine on rat embryonic development

The influence on embryonic development of nicotine and caffeine at dose levels approximating human consumption was investigated in Sprague-Dawley rats. One group of animals received nicotine administered subcutaneously by an Alzet mini-osmotic pump from gestational day 6 through 12 (25 mg over 7 days; rate 149 micrograms/hr). Control animals received physiological saline in a similar manner. A second group received a single intravenous injection of caffeine (25 mg/kg) on gestational day 6. Control animals were treated with physiological saline. A further group received both nicotine and caffeine on gestational day 6 as described for the two previous groups. There were no significant differences among any of the groups with respect to maternal weight gain, litter size, embryolethality, fetal weight, or crown-rump length. The offspring of nicotine treated animals showed a significantly higher incidence of hydrocephaly when compared to the controls, but in the combined treatment group no malformed fetuses were observed. Light microscopic examination of maternal liver, kidney and placentas revealed changes in the hepatic sinusoids, glomeruli and intervillous spaces after nicotine and combined treatment. In addition, the decidua basalis was poorly developed compared to the controls. Chorionic villi and fetal kidney appeared normal in all groups. A coteratogenic effect is not evident from these findings.     

Permanent alterations in the hypothalamic-pituitary-thyroid axis in the rat following phenytoin exposure in utero

Phenytoin exposure in utero results in permanent alterations of the hypothalamic-pituitary-thyroid axis in the rat. The DPH exposed animals have decreased weight gain, thyroxine and triiodothyronine concentrations. In addition, they have blunted thyroid-stimulating hormone responses to thyrotropin-releasing hormone, propylthiouracil challenge or thyroidectomy. The diminished pituitary response in these animals is similar to that reported in neonatal thyrotoxicosis in the rat. This may be due, in part, to structural similarities between phenytoin and the thyroid hormone.     

Hepatic insulin binding following in utero exposure to ethanol

Insulin binding to liver membranes has been studied in term fetuses of rats fed ethanol-containing liquid diet during pregnancy . Pair-fed and ad libitum-fed controls received liquid diet in which maltose-dextrins were substituted isocalorically for ethanol. Food consumption and body weigh gain of ethanol- imbibing dams were 35% and 70% less than their ad libitum counterparts respectively. Ethanol-fed rats also exhibited less gain in body weight than pair-fed controls despite isocalorically equivalent food intake. The number of live pups was not different among the various groups; however, liver weight of fetuses exposed to ethanol in utero was 47% less than those of the pups of ad libitum control dams and 28% less than those of the offspring of pair-fed control rats. Insulin binding to liver membranes of fetuses exposed to ethanol in utero was lower than that of ad libitum controls but was not significantly different from that of the pair-fed control animals. Average affinity profiles showed a reduction in K at all levels of receptor occupancy in the fetuses of ethanol-fed rats. For fetuses of the pair-fed group, K was reduced only at fractional occupancy below 20% but not at higher fractional occupancy. Because of the similarity of insulin binding in the fetuses of the ethanol-fed rats and their pair-fed counterparts, effects of ethanol on insulin binding cannot account for the reduced hepatic glycogen stores previously reported in term fetuses.     

In vitro development of the embryonic mouse inner ear following exposure to trypsin

Trypsin has been shown to disrupt normal in vitro morphogenesis of embryonic organ rudiments. Otic tissues derived from 11-, 12-, and 13-day-old mouse embryos were exposed to either Ca++- and Mg++-free PBS or 0.25% trypsin dissolved in Ca++- and Mg++-free PBS prior to explanation into organ culture. Trypsin treatment of otic explants disrupted the expression of the normal pattern of inner-ear development in vitro. There was a direct correlation between the embryonic age at time of exposure to trypsin and the severity of dysmorphogenesis of the inner ear. The younger explants showed abnormalities of both vestibular and auditory structures, whereas with increasing embryonic age, abnormalities were confined more to the auditory portion of the inner ear. The results suggest that integrity of the otocyst basal lamina and epitheliomesenchymal tissue interactions are important factors in early otic development. It is postulated that the major effect of trypsin on inner-ear morphogenesis is through disruption of these factors, which may act to regulate the progressive expression of early otic development.     

Suckling deficits in rat pups exposed to alcohol in utero

With the aid of a pair-feeding procedure, two groups of pregnant Long-Evans rats were fed a liquid diet containing 35% or 0% ethanol-derived calories during days 6-20 of gestation. A third group was allowed free access to standard lab chow and water throughout pregnancy. At 6-7 or 9-10 days of age, suckling performance by male and female offspring representing the three prenatal treatment groups was examined. The test stimulus was a 6-10-day postparturient, anesthetized dam in which milk letdown was prevented. Compared to both pair-fed and lab chow controls, alcohol-exposed animals exerted a lower maximum suckling pressure, spent less time suckling during the test session, and displayed an altered suckling pattern. These data are consistent with existing clinical and experimental evidence documenting sucking deficits following prenatal alcohol exposure and are discussed in terms of prenatal alcohol-induced CNS impairment.     

Changes in red nucleus neuronal development following maternal alcohol exposure

The red nucleus of Swiss Webster mouse fetuses was examined for morphological changes following maternal ethanol exposure. Pregnant females were given a liquid diet containing 30% or 0% ethanol-derived calories. Changes in numerical density of neurons and in neuronal nuclear volume were found in the rostral red (RR) nucleus of ethanol-exposed pups but not in the caudal red (CR) nucleus. Because of the integrative nature of the RR, changes in neuronal morphology that might relate to synaptic connections could affect the behavioral response mechanisms of these offspring.     

Altered electrical response to caffeine exposure in hypertrophied rat myocardium

We investigated the electrophysiological effects of cardiac hypertrophy induced by different experimental models. Comparison of the action potentials of hypertrophied and control rat hearts reveals a pronounced prolongation of the action potential for all types of hypertrophy. This prolongation affects the entire repolarization phase of the action potential 8 days after severe aortic constriction, after 8 days of isoproterenol treatment (5 mg/kg per day), and 3 months after an aortocaval fistula. The electrical changes associated with myocardial hypertrophy induced by pressure overload (aortic constriction) were compared with those resulting from volume overload (aortocaval fistula). Our results show that action potential alterations depend on the nature, duration, and severity of the work load. Thus, pressure overload is more potent to induce these modifications. In the hearts subjected to pressure overload, action potential alterations appear more rapidly and are more marked for the same degree of hypertrophy than those of the volume-hypertrophied myocardium. Furthermore, such data also demonstrate that the early alteration of the action potential during the development of compensatory hypertrophy is a prolongation of the later phase of repolarization (phase 3), without prolongation of the other repolarization phases (1 and 2). This change appears 3 days after aortic constriction, 1 month after coronary artery ligation (in the healthy part of the left ventricle), and 1 month after an aortocaval fistula.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hematological toxicology following embryonic exposure to aflatoxin-B1

The influence of embryonic exposure to aflatoxin-B1 (AF-B1) upon the erythroid system of the maturing chicken was examined using a variety of assays. Since the chick embryo is known to possess mixed-function oxidase activity, this animal serves as an excellent model system for studies of human fetal toxicology. AF-B1 (0.1 microgram) was administered to either 6- or 12-day embryos by the air sac method. This level of AF-B1 was highly mutagenic and was found to induce an average of 10.6 sister chromatid exchanges (SCEs) per cell compared with 1.8 SCEs per cell for the acetone control solvent. Despite selection against treated embryos through acute and chronic embryonic toxicity, hatched chicks from AF-B1 treatment groups exhibited erythroid anemia when compared to the acetone controls. Cell count, hematocrit, and hemoglobin concentration were all significantly reduced in the 12-day AF-B1 treatment groups compared with controls. Both sexes were equally affected. While the number of peripheral erythrocytes was reduced following exposure to AF-B1, the differentiation status of erythrocytes was apparently unaltered. Mean cell volume, percentage of circulating reticulocytes, and incidence of an erythroid differentiation marker, chicken fetal antigen, were parameters in which no treatment effects were observed. An apparent maturation effect was noted since adult hematocrits were similar between control and treatment groups. Possible explanations for this age effect are discussed. The ability to detect significant posthatch erythroid toxicity following embryonic exposure to mutagenic levels of AF-B1 suggests the importance of this general approach to perinatal carcinogenic evaluation.     

Neuron development in the superior colliculus of the fetal mouse following maternal alcohol exposure

Pregnant Swiss Webster mice were given a liquid diet with ethanol (EtOH) or isocaloric amounts of maltose dextrin on gestation day (GD) 0 through 18. On GD 18, maternal blood samples were obtained. Fetuses were then removed and fetal brains were prepared for light microscopy. Fetal weight was reduced in the EtOH-exposed group. The ratio of midbrain cross sectional area to cerebral aqueduct was reduced in the ethanol group, while the density of neuronal nuclear population in both the dense outer layer (DS) and sparse inner layer (SS) of the developing superior colliculus was increased. Mean nuclear volume was decreased in the SS.     

Gender differences in transcriptional signature of developing rat testes and ovaries following embryonic exposure to 2,3,7,8-TCDD

Dioxins are persistent organic pollutants interfering with endocrine systems and causing reproductive and developmental disorders. The objective of our project was to determine the impact of an in utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on reproductive function of male and female offspring in the rat with a special emphasis on the immature period. We used a low dose of TCDD (unique exposure by oral gavage of 200 ng/kg at 15.5 days of gestation) in order to mirror a response to an environmental dose of TCDD not altering fertility of the progeny. We choose a global gene expression approach using Affymetrix microarray analysis, and testes of 5 days and ovaries of 14 days of age. Less than 1% of the expressed genes in gonads were altered following embryonic TCDD exposure; specifically, 113 genes in ovaries and 56 in testes with 7 genes common to both sex gonads. It included the repressor of the aryl hydrocarbon receptor (Ahrr), the chemokines Ccl5 and Cxcl4 previously shown to be regulated by dioxin in testis, Pgds2/Hpgds and 3 others uncharacterized. To validate and extend the microarray data we realized real-time PCR on gonads at various developmental periods of interest (from 3 to 25 days for ovaries, from 5 to the adult age for testes). Overall, our results evidenced that both sex gonads responded differently to TCDD exposure. For example, we observed induction of the canonic battery of TCDD-induced genes coding enzymes of the detoxifying machinery in ovaries aged of 3-14 days of age (except Cyp1a1 induced at 3-10 days) but not in testes of 5 days (except Ahrr). We also illustrated that inflammatory pathway is one pathway activated by TCDD in gonads. Finally, we identified several new genes targeted by TCDD including Fgf13 in testis and one gene, Ptgds2/Hpgds regulated in the two sex gonads.     

Combined effects of radiation and caffeine on embryonic development in mice

The combined effect of radiation and caffeine has been studied in mouse embryos. Radiation and/or caffeine were administered to ICR mice on Day 11 of gestation. Intrauterine death, gross malformation, and fetal body weight were selected as indicators of effects. Doses of whole-body gamma irradiation were 0.5 to 2.5 Gy and those of caffeine were 100 and 250 mg/kg maternal body wt. Intrauterine mortality increased with increasing radiation dose; this trend was more remarkable in combination with caffeine. Gross malformations such as cleft palate and defects of forelegs and hindlegs appeared frequently in the fetuses treated with both radiation and caffeine. Decreased fetal weight was observed even in mice treated with 0.5 Gy of radiation or 100 mg/kg caffeine. There was a linear relationship between dose and reduction of fetal weight. The fetal weight was a sensitive, precise, and easy-to-handle indicator for the effects of growth retardation. Intrauterine mortality and frequencies of cleft palate and defects of forelegs and hindlegs were higher than the sum of those induced by radiation and by caffeine separately. The results indicated that the combined action of radiation and caffeine on intrauterine death and malformations was synergistic.     

Biochemical alterations in rat fetal liver following in utero exposure to di(2-ethylhexyl)phthalate (DEHP)

Oral administration of DEHP, 1000 mg/kg body weight, to rats daily from 6 to 15 day of gestation resulted in retardation of fetal growth and increase in fetal liver weight which contained significant quantities of DEHP. The activities of mitochondrial succinate dehydrogenase, malate dehydrogenase, cytochrome c oxidase and adenosine triphosphatase were decreased in fetal liver. The data indicate that exposure of mothers to DEHP during pregnancy could adversely affect the fetal livers by interfering with bioenergetics of the cell.     

蛙的早期胚胎发育

根据多年来对一些经济蛙类的繁殖习性及胚胎发育的观察,并结合国内外有关的研究报道,介绍了两栖动物的繁殖类型及蛙类早期胚胎发育的过程,为教学提供有益的参考资料。     

In utero and childhood exposure to alcohol and old age mortality: Evidence from the temperance movement in the US

Previous research suggests the relevance of in-utero insults and early-life circumstances for a wide array of life cycle outcomes. This research note joins this strand of studies by exploring the long-run mortality effects of in-utero and early-life exposure to alcohol accessibility. In so doing, we take advantage of the prohibition movement during the early part of the twentieth century that generated quasi-natural reductions in alcohol consumption. We use Social Security Administration Death Master Files linked to the full-count 1940 census and compare the longevity of male individuals exposed to the prohibition during in-utero and early childhood (1900–1930) as a result of statewide and federal alcohol ban to those wet counties after the law change to before. The results suggest an intent-to-treat effect of 0.17 years higher longevity as a result of prohibition. A back-of-an-envelope calculation suggests a minimum treatment-on-treated effect of 1.7 years impact. Furthermore, we show that these effects are not driven by other county-level demographic and socioeconomic changes, endogenous selection of births, and preexisting trends in the outcome. Our findings contribute to the growing body of research that explores the in-utero and childhood circumstances on long-term health outcomes.