Radiation effects on development

It has been widely reported that prenatal exposure to ionizing radiation can interfere with embryonic and fetal development, depending on dose and gestational age in which exposure occurs. According to several studies on animal models, different well-defined stages during prenatal life can be distinguished in relation to teratogenic effects. During the preimplantation stage, elevated doses of radiation can result in abortion, while lower doses may produce genomic damage that is usually repaired. On the other hand, during the organogenesis stage in mice (embryonic day 6.5 [E6.5] to E13.5), irradiation is associated with increased incidence of malformation and intrauterine growth restriction (IUGR). Later exposure is linked to brain damage. Doses used in animal studies are generally higher than those used for diagnostic procedures in humans. Usually, radiation exposure to diagnostic range (<0.05 Gy = 5 rads) is not associated with an increased risk of congenital anomalies. In human studies, elevated doses produce adverse outcomes, depending on stage of development, as in animal studies. Blastogenesis (up to two weeks) is associated with failure to implant or no significant health effects. An increased risk of malformation and growth retardation can be observed for two to seven weeks exposure (organogenesis stage), while exposure at later stages (fetogenesis) is mainly associated with brain damage. In this review we focus on the relevance of estimating the cumulative dose of radiation to the fetus and the gestational age in which exposure occurs, to provide appropriate counseling to pregnant women.     

Neuropeptide effects on brain development

Peptides which act as neurotransmitters or neuromodulators in the adult nervous system exert influences on brain development. Altering the levels of neuropeptide to which a developing animal is exposed produces a wide variety of physiological and behavioral effects which are apparent in adulthood. Many of the developmental effects involve neural systems in which the neuropeptide plays a role in the adult.     

Light quality effects on corn chloroplast development

Corn was grown under greenhouse and controlled light quality conditions incluing full spectrum, red (R), and far-red (FR) sources. Young leaf samples were analyzed for pigments, pigment-proteins, membrane polypeptides, and ultrastructure. Chloroplast development in full spectrum white light was similar to that found in R but different from that found in FR plus low R. Compared to greenhouse and R, FR plus low R (670-760) repressed the formation of photosystem I reaction center protein (CP1 + CP1a) and enhanced those of photosystem II (CPa) in both bundle sheath and mesophyll cells. Photosystem II polypeptides were present in both cell types, with the 46 and 34 kilodalton proteins predominant in mesophyll cells. Bundle sheath cells contained relatively more of the 51 kilodalton and less of the 46 kilodalton proteins. However, they also contained measurable amounts of ribulose bisphosphate carboxylase which may interfere with estimates of the 51 kilodalton protein.     

The effects of alcohol on fetal development

Prenatal exposure to alcohol has profound effects on many aspects of fetal development. Although alterations of somatic growth and specific minor malformations of facial structure are most characteristic, the effects of alcohol on brain development are most significant in that they lead to substantial problems with neurobehavioral development. Since the initial recognition of the fetal alcohol syndrome (FAS), a number of important observations have been made from studies involving both humans and animals. Of particular importance, a number of maternal risk factors have been identified, which may well be of relevance relative to the development of strategies for prevention of the FAS as well as intervention for those who have been affected. These include maternal age >30 years, ethnic group, lower socioeconomic status, having had a previously affected child, maternal under-nutrition, and genetic background. The purpose of this review is to discuss these issues as well as to set forth a number of questions that have not adequately been addressed relative to alcohol's effect on fetal development. Of particular importance is the critical need to identify the full spectrum of structural defects associated with the prenatal effects of alcohol as well as to establish a neurobehavioral phenotype. Appreciation of both of these issues is necessary to understand the full impact of alcohol on fetal development.     

The legacy of lithium effects on development

The simple element lithium causes specific effect on early embryonic development. In amphibians, treatment during early cleavage enhances anterior and dorsal development at the expense of posterior and ventral development. Conversely, treatment at late cleavage reduces head development. While an effect of lithium on the phosphoinositide cycle was suspected, the enhancement of dorsoanterior development is now thought to result primarily from stimulation of the Wnt/beta-catenin pathway. The multiple uses of this pathway in development may account for lithium's various specific effects.     

Prenatal epoxiconazole exposure effects on rat postnatal development

Although some studies have pointed out to embryo/fetal toxicity, knowledge about the potential toxicity of the fungicide epoxiconazole is still limited. Once the results of these previous studies have raised some concern, this study studied the effects of epoxiconazole maternal exposure on the physical endpoints in the development of rat pups. To accomplish that, the effects of epoxiconazole (50.0, 100.0, and 150.0 mg/kg) were examined when rats were exposed at two different developmental stages: during the first 6 days of pregnancy or in the organogenesis period (6-15 days). After parturition, pups were tested for growth and maturational milestones. Maternal exposure to the fungicide, independently of phase, resulted in significantly early mean time to vaginal opening and delayed time to testes descent in pups. Weight gain rate in pups and their mothers was not affected for the tested exposure period. The findings of this study emphasize that epoxiconazole maternal exposure may lead to alterations in developmental patterns in nursing pups, consistent with the known influence of epoxiconazole on steroid hormone synthesis.     

Light effects on development of an indeterminate plant

The peanut (Arachis hypogaea L.) plant is indeterminate in growth habit and day-neutral with respect to flower initiation. The Spanish-type cultivar used in this study begins flowering 3 to 4 weeks from planting under optimum environmental conditions. In this study, irradiance and photoperiod were used to alter the development of the peanut plant. Plants grown at low irradiance (300 microeinsteins per square meter per second) had the same number of leaves as the plants grown at high irradiance (500 microeinsteins per square meter per second), but they had a larger leaf surface area and were taller than plants grown at the high irradiance. However, flowering and other reproductive components (pegs, pods, and seeds) were reduced at low irradiance. Comparison of 8-, 12-, and 16-hour photoperiods at the high irradiance showed that the 16-hour photoperiod produced the largest amount of vegetative, but least amount of reproductive components. The plants grown at 8-hour photoperiod had one-third as much total leaflet area as plants grown at 16 hours, but six times more weight of mature seeds. The larger amount of photosynthetic surface (leaf area) did not result in more reproductive growth. The results indicate that the peanut plant may readily redistribute its available assimilates between vegetative and reproductive growth in response to irradiance and photoperiod.     

The effects of nuclear mutation on chloroplast development

Summary Under greenhouse conditions the dark green wild type (su/su) tobacco grows 2–3 times faster than the yellow mutant (Su/su) and contains five-fold more chlorophyll. On a fresh weight basis, however, both genotypes contain similar amounts of RuBPCase and fraction 11 protein in approximately equal proportion and have similar levels of 70s and 80s ribosomes. When seedlings are cultured on agar medium supplemented with sucrose and equal concentrations of IAA and kinetin or kinetin alone, a drastic reduction of RuBPCase and free 70s ribosomes, but not of chlorophyll content, were observed. Moreover, albino (Su/Su) seedlings developed on supplemented media still contain appreciable amounts of RuBPCase and free 70s ribosomes although chlorophyll levels are extremely low indicating no correlation between RuBPCase and chlorophyll content. RuBPCase crystallized from both wild type and yellow mutant plants seem to have identical composition and structure when examined by isoelectric focusing, amino acid analysis or peptide mapping techniques. The slow-growing yellow mutant is apparently deficient only in chlorophyll of the light harvesting chlorophyll-protein complex but with no alteration of the protein moiety or chlorophyll a/b ratio.     

Evaluation of radon effects on lung cancer development

In order to evaluate the effect of indoor exposure to radon and thoron on the development of lung cancer in the population of two towns of Sverdlovsk Region, epidemiologic studies were conducted using a multifactarial method of analysis. Both towns, Pervouralsk and Karpinsk, are located within the geological area with the gamma-radiation exposure dose ranging from 5 to 12 mu r/hr, and are characterized by an increased cancer incidence rate--323.1 and 364.6 cases per 100,000 of population, respectively. The mean values of the voluminous indoor activity (VA) of radon in Pervouralsk and Karpinsk were 23 and 75 Bq/m3 (with maximal indices of radon VA being 395 and 739 Bq/m3), equivalent equilibrium concentrations (EEC) of residential radon and thoron were 0.6 and 2.5 Bq/m3 (maximal indices of EEC of thoron being 5 and 13 Bq/m3), respectively. The results of multifactorial analysis of 22 different lung cancer risk factors carried out using the pattern recognition method proved that the contribution of thoron and radon in the development of lung cancer in the population of Pervouralsk and Karpinsk was not significant--0.5 and 0.6%, respectively. The calculations performed in a monofactorial model of risk evaluation BEIR VI gave different results--11-16% and 35-52% for the towns of Pervouralsk and Karpinsk, respectively. The discussion of the results provides arguments for the reliability and adequacy of the application of multifactorial method of radiation risk evaluation as compared to the traditionally applied monofactorial method.     

Genomic imprinting effects on brain development and function

In a small fraction of mammalian genes--at present estimated at less than 1% of the total--one of the two alleles that is inherited by the offspring is partially or completely switched off. The decision as to which one is silenced depends on which allele was inherited from the mother and which from the father. These idiosyncratic loci are known as imprinted genes, and their existence is an evolutionary enigma, as they effectively nullify the advantages of diploidy. Although they are small in number, these genes have important effects on physiology and behaviour, and many are expressed in the brain. There is increasing evidence that imprinted genes influence brain function and behaviour by affecting neurodevelopmental processes.     

Sugar effects on early seedling development in Arabidopsis

Sugars affect a broad variety of processes, from growth and development to gene expression. Although it has already been shown that sugars act as signaling molecules, little is known about the mechanisms by which plants respond to them. Much progress has been made on understanding sugar sensing and signaling thanks to the analysis of mutants with abnormal sugar response. Some of the genetic strategies applied are based on the inhibitory effect of sugar on post-germinative development of Arabidopsis thaliana. High concentrations of exogenous sugars delay germination and arrest early growth, preventing seedlings from expanding cotyledons and developing true leaves and an extensive root system. The characterization of several Arabidopsis mutants identified for their altered sugar sensitivity has disclosed a network in which sugars and plant hormones cooperate to control seedling development. Remarkably, many mutations turned out to be novel alleles of hormone-related genes, mainly ABA and ethylene. The aspects described above, emphasizing the connections between sugar and plant hormones revealed by mutants derived in seedling-based screens, are reviewed in this paper.     

Magnetic fields and time dependent effects on development

Pulsed, extremely-low-frequency electromagnetic fields caused a significant increase in abnormalities in the developing chick embryo. The effect was observed when the field was presented during the first 24 h of incubation; no significant effect was observed with exposure from 24 to 48 h of incubation.     

The effects of nicotine on human fetal development

Maternal smoking during pregnancy continues to represent a major public health concern. Nicotine is extremely harmful to the developing fetus through many different mechanisms, and the harms increase with later gestational age at exposure. Pregnancies complicated by maternal nicotine use are more likely to have significant adverse outcomes. Nicotine‐exposed children tend to have several health problems throughout their lives, including impaired function of the endocrine, reproductive, respiratory, cardiovascular, and neurologic systems. Poor academic performance and significant behavioral disruptions are also common, including ADHD, aggressive behaviors, and future substance abuse. To diminish the adverse effects from cigarette smoking, some women are turning to electronic cigarettes, a new trend that is increasing in popularity worldwide. They are largely perceived as being safer to use in pregnancy than traditional cigarettes, although there is not adequate evidence to support this claim. At this time, electronic cigarette use during pregnancy cannot be recommended. Birth Defects Research (Part C) 108:181–192, 2016. © 2016 Wiley Periodicals, Inc.     

Aflatoxin M1 effects on Xenopus laevis development

BACKGROUND: The principal Aflatoxin B(1) (AFB(1)) hydroxylated metabolite excreted in milk is Aflatoxin M(1) (AFM(1)) classified in group 2B by the International Agency for Research on Cancer (IARC). Human exposure to AFM(1) is due to the consumption of contaminated dairy products and partly to endogenous production through AFB(1) liver metabolism. METHODS: Since no data are available on AFM(1) embryotoxicity, its lethal and teratogenic potential was investigated using the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). Stage-8 blastulae were exposed to AFM(1) at 1, 4, 16, 64, and 256 microg/L concentrations until stage 47, free-swimming larva. RESULTS: A slight increase of mortality and malformed larva percents was found in AFM(1)-exposed groups but these differences were not statistically significant in comparison with the controls. CONCLUSIONS: Therefore, AFM(1) is a non-embryotoxic compound when evaluated with a FETAX model at concentrations under the conditions tested. However, AFM(1) merits further studies using mammals as experimental models to identify a possible risk during human pregnancy.     

三甲双酮对斑马鱼胚胎早期发育的影响

针对抗癫痫药物的临床神经性毒副作用及致畸性,以三甲双酮为探针药建立了抗癫痫药毒性的斑马鱼胚胎模型。结果显示,斑马鱼胚胎暴露于三甲双酮后出现浓度依赖性的畸形和死亡。畸形表型有生长迟缓,脑区、眼和听囊变小,半规管和耳石受损,以及心血管系统异常。这些表型与临床病例和文献报道很相似。毛细胞染色显示听囊ML2神经丘毛细胞数明显减少。原位杂交检测发现脑标志基因zic1和xb51、自噬基因atg5的表达图式发生了异常变化。RT-PCR检测显示听觉基因val和hmx2的表达水平也发生了异常变化。这些结果提示脑组织和控制身体平衡及听力的神经感受器是三甲双酮的主要毒性靶位。斑马鱼胚胎和幼体可以模拟三甲双酮对哺乳动物的致畸和神经毒性反应。