Incidence Of Developmental Abnormalities Research Articles

Embryonic and larval development of yellow perch (Perca flavescens) and its sensitivity to incubation temperature.

The ontogenetic development in teleost fish is sensitive to temperature, and the developmental rate has a direct relationship with the environmental temperature within a species' thermal tolerance limit. Temperature determines time to and survival at hatching. Yellow perch is a North American species of ecological and commercial importance, and its phenology is vulnerable to climate change. The embryonic development of yellow perch was comparable to closely related members of the family Percidae. Developmental progression was fastest at 18°C and slowest at 12°C, with medial progression at 15°C. Time to hatch and swim-up, feeding onset, and exogenous feeding phases were different across all incubation temperatures regardless of a gradual post-hatch warming of the 12 and 15°C groups to a common garden temperature of 18°C. Incubation temperature may lower the rate of survival to hatch at 15°C and had complex impacts on developmental abnormalities. Temperature had significant effects on the development rate, time of hatch, survival, and incidence of developmental abnormalities. Early ontogenetic thermal history in ectotherms is an important factor determining phenotypic variation. It will be important to link the thermally induced changes in development described here to the physiological and morphological differences and to link the developmental abnormalities to functional performance.

Influencing factors of the neurodevelopment of high-risk infants

BackgroundHigh-risk infants refer to newborns exposed to high-risk factors in the prenatal, natal or postnatal period. High-risk infants are at high risk of developmental retardation, and early identification of developmental...

Plastic rates of development and the effect of thermal extremes on offspring fitness in a cold-climate viviparous lizard.

Populations at the climatic margins of a species' distribution can be exposed to conditions that cause developmental stress, resulting in developmental abnormalities. Even within the thermal range of normal development, phenotypes often vary with developmental temperature (i.e., thermal phenotypic plasticity). These effects can have significant consequences for organismal fitness and, thus, population persistence. Reptiles, as ectotherms, are particularly vulnerable to thermal effects on development and are, therefore, considered to be at comparatively high risk from changing climates. Understanding the extent and direction of thermal effects on phenotypes and their fitness consequences is crucial if we are to make meaningful predictions of how populations and species will respond as climates warm. Here, we experimentally manipulated the thermal conditions experienced by females from a high-altitude, cold-adapted population of the viviparous skink, Niveoscincus ocellatus, to examine the consequences of thermal conditions at the margins of this population's normal temperature range. We found strong effects of thermal conditions on the development of key phenotypic traits that have implications for fitness. Specifically, we found that offspring born earlier as a result of high temperatures during gestation had increased growth over the first winter of life, but there was no effect on offspring survival, nor was there an effect of developmental temperature on the incidence of developmental abnormalities. Combined, our results suggest that advancing birth dates that result from warming climates may have positive effects in this population via increased growth.

Effects of ashes from a Brazilian savanna wildfire on water, soil and biota: An ecotoxicological approach

Wildfire is very common in Brazilian savannas, and its effects on water, soil and aquatic/soil organisms are poorly understood. In this study, we observed the effects of fire, especially of ashes, on surface soil and subsurface water in a typical Brazilian savanna (Cerrado sensu strictu) for one year. Soil analyses (pH, organic matter content, potential acidity, K, Ca, Mg and P) and subsurface water analyses (NO3−, PO43ˉ Mg2+, Ca2+ and K+) were assessed. We evaluated the ecotoxicological effects of ashes on three different endpoints and species, in fish Danio rerio (embryonic development), aquatic snail Biomphalaria glabrata (reproduction) and a soil species Enchytraeus sp. (reproduction). We found a higher amount of exchangeable cations and organic matter content in short-term fire effects on soil, but the higher availability of nutrients did not affect the soil pH in field plots. The effects of ashes on soil and subsurface water did not persist for one-year post-fire, except for organic matter content in burned areas. No toxic effects were observed on hatching success and incidences of developmental abnormalities in D. rerio embryos. However, ash input had adverse effects on reproduction in snails and enchytraeids. We reported a statistically significant decrease in snail eggs exposed to the 50g.L−1 and 100g.L−1 of ashes after four weeks (p<0.05, Dunnett's test and Tukey test). Enchytraeus sp. reproduction was negatively influenced by the natural soil, which presents high acidity, and also when exposed directly to the ashes from burned area, suggesting that pH and other ash compounds may limit the growth of enchytraeids. More studies in burned areas are strongly encouraged, addressing the potential important routes of exposure to ashes in order to understand the impact of intense fires on soil and aquatic biota in tropical savannas.

Influence of metal(loid) bioaccumulation and maternal transfer on embryo-larval development in fish exposed to a major coal ash spill

In December 2008, an earthen retaining wall at the Tennessee Valley Authority (TVA) Kingston Fossil Fuel Plant failed and released 4.1 millionm3 of coal ash to rivers flowing into Watts Bar Reservoir in east Tennessee, United States (U.S.). As part of a comprehensive effort to evaluate the risks to aquatic resources from this spill – the largest in U.S. history – we compared bioaccumulation and maternal transfer of selenium (Se), arsenic (As), and mercury (Hg) in adult redear sunfish (Lepomis macrolophus), collected two years after the spill from both coal-ash exposed and non-exposed areas of the Emory and Clinch Rivers, with the success of embryo-larval development in their offspring. Whole body and ovary concentrations of Se in female sunfish at three study sites downstream of the spill were significantly elevated (site means=4.9–5.3 and 6.7–9.0mg/kg d.w. whole body and ovary concentrations, respectively) compared with concentrations in fish from reference sites upstream of the spill site (2.2–3.2mg/kg d.w. for whole bodies and 3.6–4.8mg/kg d.w. for ovaries). However, Se concentrations in coal ash-exposed areas remain below proposed U.S. Environmental Protection Agency (USEPA) criteria for the protection of aquatic life. Site-to-site variation in fish concentrations of As and Hg were not well-correlated with ash-exposure, reflecting the multiple sources of these metal(loid)s in the affected watersheds. In 7-day laboratory tests of embryos and larvae derived from in vitro crosses of eggs and sperm from these field-collected sunfish, fertilization success, hatching success, embryo-larval survival, and incidences of developmental abnormalities did not differ significantly between ash-exposed and non-exposed fish. Furthermore, these developmental endpoints were not correlated with whole body or ovary concentrations of Se, As, or Hg in the maternal fish, or with fish size, ovary weight, or gonadal-somatic indices. Results from this and related studies associated with the Kingston coal ash spill are consistent with proposed USEPA fish-based water quality criteria for Se, and to date continue to suggest that long-term exposures to sediment containing residual ash may not present a significant chronic risk to fish populations exposed to this major coal ash release.

Effects of Sediment Containing Coal Ash from the Kingston Ash Release on Embryo-Larval Development in the Fathead Minnow, Pimephales promelas (Rafinesque, 1820)

The largest environmental release of coal ash in US history occurred in December 2008 with the failure of a retention structure at the Tennessee Valley Authority Kingston Fossil Fuel Plant in East Tennessee. A byproduct of coal-burning power plants, coal ash is enriched in metals and metalloids such as selenium and arsenic with known toxicity to fish embryonic and larval life stages. The early development of fish embryos and larvae during contact exposures to river bottom sediments containing up to 78 % coal ash from the Kingston spill was examined in 7-day laboratory tests with the fathead minnow (Pimephales promelas). No significant effects were observed in hatching success, incidences of developmental abnormalities, or embryo-larval survival. Results suggest that direct exposures to sediment containing residual coal ash from the Kingston ash release may not present a significant risk to fish eggs and larvae in waterways affected by the coal ash spill.

Are medicinal plants polluted with phthalates?

Phthalic acid esters (PAEs) have been employed in polymer materials as a plasticizer to form them more flexible, adhesive, and soluble. These compounds are mainly used in paints, varnishes, personal cares, cosmetics, paper coatings, and adhesives even in bottled waters, shampoo, body deodorant, hairspray, and gels. Phthalates are able to possess remarkable toxic variations depending on their structures. So far, Di-(2-EthylHexyl) Phthalate DEHP and Di-n- Butyl Phthalate DBP have been found to cause reproductive and developmental toxicities. The U.S. Environmental Protection Agency (EPA) classified DEHP as probable human carcinogen. To the best of our knowledge, phthalates showed diverse toxicity profiles according to their structures in the liver, kidneys, thyroid, and testes, which are involved in general toxicity. Furthermore, they are introduced as hormonally-active agents, because they can interfere with the endocrine system in human. Incidence of developmental abnormalities (like skeletal malformations and cleft palate, and undescended testes, lowering testes weight and anogenital distance) seems increasing via high exposure to phthalate metabolites. Although, increasing the capacity for phthalate free plasticizer productions is the first step to restrict the distribution of these toxic manmade compounds, finding the new ways for phthalate absorption from the soil in agricultural fields may have benefits. Also, evaluation and examination of diverse sources of medicinal and food plants to determine the level of phthalate accumulation in their organs are extremely recommended to avoid creating toxicity particularly in reproductive systems.

120 THE DEVELOPMENTAL COMPETENCE OF TADPOLES PRODUCED IN VITRO FROM THE ENDANGERED DUSKY GOPHER FROG (RANA SEVOSA) USING EXOGENOUS HORMONE TREATMENT

Dusky gopher frogs once existed throughout the states of Mississippi, Alabama and Louisiana. Presently, the USA Fish and Wildlife Service estimates that there are less than 100 frogs left in the wild, with almost all of these residing in a single pond in Mississippi, making the dusky gopher frog America's most endangered frog species. Their habitat has been threatened by residential and forestry development, as well as from fire suppression and the decline of gopher tortoises, whose burrows the frogs use for shelter. The USA Fish and Wildlife Service brought the first dusky gopher frogs into captivity in 2001 and they have been kept at the Memphis Zoo since 2003 and at Omaha's Henry Doorly Zoo since 2004. Natural breeding attempts in captivity have been unsuccessful despite efforts to artificially mimic what is known to be the appropriate seasonal environmental (e.g. light, humidity, temperature) and social cues (e.g. calls from wild frogs during the breeding season) that stimulate reproduction in situ. Also, there was a concern about the incidences of abnormalities (e.g. spindly legs) from inadequate husbandry conditions (e.g. nutritional deficiencies) or diseases in tadpoles and froglets produced ex situ (e.g. dermomycoides). The objectives of this study were (1) to examine the developmental competence of tadpoles produced by exogenous hormone treatment for IVF to complete normal metamorphosis into viable froglets ex situ and (2) to determine the incidence of developmental abnormalities or dermomycoides in the froglets produced ex situ. Males and females were first separated by the identification of black male nuptial pads used during amplexus. Males and females were stimulated to spermiate and ovulate, respectively, using a variation of a standard amphibian hormonal stimulation protocol (Kouba et al. 2012 Reprod. Fertil. Dev. 24). As a result, more than 1460 viable tadpoles (61% of fertilized eggs) were produced from 18 segregated genetic pairings. To date, 602 (41%) of the tadpoles have completed normal metamorphosis into viable froglets (over 6 times the known existing population in situ), 51% were either culled to examine for dermomycoides or died for a variety of known (accidental) and unknown reasons (abnormal appendage development accounting for less than 7%) and 8% have yet to metamorphose after 9 months. The incidence of dermomycoides in the culled individuals was 100%; however, a study being conducted concurrently in their native habitat has confirmed that the organism does exist in situ with the dusky gopher frogs, which act as natural carriers. Efforts are currently in place to establish reintroduction programs for the dusky gopher froglets produced ex situ to increase the dwindling wild population now that tadpoles produced by IVF have been shown to be developmentally competent. In conclusion, IVF can be used to produce tadpoles of the dusky gopher frog with a low incidence of abnormalities, but the tadpoles were found to be carriers of the organism dermomycoides similar to their counterparts in the wild.

340 EPIGENETIC ANALYSIS OF DEVELOPMENTALLY IMPORTANT GENES IN BOVINE OOCYTES OF DIFFERENT ORIGINS

A critical step in assisted reproductive technologies (ART) is the IVM of oocytes. The quality of the oocyte is crucial for successful fertilization and subsequent embryo development. Studies in bovine ART, and epidemiological studies in children from ART, reveal a degree of abnormal development thought to be primarily caused by aberrant DNA methylation patterns in imprinted and non-imprinted genes. Due to the inherent similarities in bovine and human preimplantation embryonic development, bovine oocyte and embryo development is increasingly being used as a model for human development. The goal of this project is to investigate the effects of specific IVM conditions on the DNA methylation profile of bovine oocytes and early embryos and to determine the relationship between DNA methylation and mRNA expression for selected developmentally important genes (PEG3, IGF2R, SNRPN, GDF9, Glut8, PRDX1, Dnmt1A and Dnmt3a/b). Two different IVM systems have been established, the first is the routinely used TCM-199 medium at 39°C, 5% CO2 in air, the second uses synthetic oviduct fluid medium (SOF) as the basic medium with minor modifications (10 mM glucose, 1 mM glutamine) at 39°C, 5% CO2 and reduced oxygen tension (5%). Oocytes for IVM were retrieved by slicing of ovaries collected from local slaughterhouses. Successful maturation was confirmed by extrusion of the first polar body for 78% (TCM) and 72% (SOF) of the oocytes, respectively. Results of quantitative real-time PCR experiments indicate that transcripts of the maternally imprinted gene PEG3 and the paternally imprinted gene IGF2R as well as transcripts of other developmentally important genes (GDF9, PRDX1 and Glut8) are present in immature and IVM oocytes and are applicable targets for further expression and methylation studies. Relative quantification of mRNA transcripts normalised to an external standard revealed that, while expression of the maternally imprinted PEG3 gene is lower in all groups of oocytes (immature: 9.8, matured in TCM: 3.3, and in SOF: 6.4), compared to the paternally imprinted IGF2R (immature: 29.3, TCM: 14.2, SOF: 19.2), no significant difference between the both groups of IVM oocytes could be detected. However, determination of specific effects of IVM will require more replicates and the comparison with IVM oocytes. This is currently underway and together with the ongoing methylation analysis based on the novel identification of differentially methylated regions in bovine imprinted genes, this study will provide deeper insight into the epigenetic profile of bovine oocytes as a potential causative mechanism implicated in the increased incidence of developmental abnormalities in human and bovine ART. Funded by DFG Research Unit Germ Cell Potential.

Developmental effects of bioaccumulated selenium in eggs and larvae of two salmonid species

Elevated concentrations of Se have been detected in cold, flowing water habitats near uranium and coal mines in Canada. Fish from these systems have concentrations of Se in their tissues that exceed toxic effect thresholds that have been established for warm-water fishes. However, the applicability of toxic effect thresholds and guidelines to cold water, lotic habitats is a matter of contention in the literature since most cases of Se toxicosis have been documented in standing, warm-water systems. To examine the possibility of impaired reproduction in wild rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinusfontinalis) near coal mining activity in the northeastern slopes region of Alberta, Canada, spawn from both species were collected from exposure and reference sites. Gametes were fertilized in the laboratory, reared to the swim-up stage, and examined for deformities. A significant relationship was observed for rainbow trout between the amount of Se in eggs and the incidence of developmental abnormalities, specifically craniofacial defects, skeletal deformities, and edema. These associations approximate exponential functions with probabilities that 15% of the population would be affected occurring between 8.8 and 10.5 microg Se per gram of wet egg weight, based on probit analysis. These relationships are similar to those described for centrarchids inhabiting a seleniferous warm-water lake. No such relationships were established for brook trout.

Multidrug resistance in the embryos and larvae of the mussel Mytilus edulis

Cells exhibiting the multidrug resistance (MDR) phenotype demonstrate a decreased intracellular drug accumulation due to an active outward transport and decreased intracellular flux. This study demonstrates the inhibition of MDR in mussel ( Mytilus edulis) embryos and larvae based on a simple bioassay. The development of embryos was assessed and abnormalities identified at key stages of development, including gastrulation, trochophore and prodissoconch stages. The incidence of developmental abnormalities was significantly increased in the presence of vinblastine, MMS, chloroquine, mitomycin-C, cadmium chloride and colchicine, compared to clean seawater. Consistently, there was a further increase in the number and severity of deformities observed when each toxin was added in the presence of verapamil. Larval growth was also significantly impaired in the presence of verapamil. Increased accumulation of fluorescent MDR dyes, such as rhodamine B, has been measured and shown to be verapamil sensitive. This bioassay encompasses a period of intense cellular activity during which the impairment of a number of critical processes results in abnormal growth and development.

Effects of 3,3′,4,4′,5‐pentachlorobiphenyl and 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin injected into the yolks of double‐crested cormorant (Phalacrocorax auritus) eggs prior to incubation

AbstractDouble‐crested cormorant (Phalacrocorax auritus) eggs were injected with either 3,3′,4,4′,5‐pentachlorobiphenyl (polychlorinated biphenyl [PCB] 126; 70‐698 μg/kg egg) or 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD; 1.3‐11.7 μg/kg egg) prior to incubation. These compounds were injected into the yolks of cormorant eggs collected from incomplete clutches at isolated colonies on Lake Winnipegosis, Manitoba, Canada. Eggs were incubated for approximately 26 to 28 d. After hatching the brain, bursa, heart, liver, and spleen were dissected and weighed. Torsos were preserved in formalin for examination of the gonads. Median lethal doses (LD50s) calculated from mortality data at hatching were 177 and 4.0 μg/kg egg for PCB 126 and TCDD, respectively. No significant differences were found in the incidence of developmental abnormalities in any of the treatment groups. Bursa weights were significantly less in the greatest (11.7 μg/kg egg) TCDD group compared to the vehicle control group. Spleen weights were significantly less in the 349 μg PCB 126/kg egg and the 5.4 and 11.7 μg TCDD/kg egg groups when compared to the vehicle control group. No histological alterations of the gonads were found. Hepatic ethoxyresorufin‐O‐deethylase activity in all PCB 126 and TCDD dose groups was significantly greater compared to the control activity. The toxic equivalency factor for PCB 126 was 0.02.

Effects of 3,3′,4,4′,5‐pentachlorobiphenyl (PCB 126), 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD), or an extract derived from field‐collected cormorant eggs injected into double‐crested cormorant (Phalacrocorax auritus) eggs

AbstractDouble‐crested cormorant (Phalacrocorax auritus) eggs were injected with either 3,3′,4,4′,5‐pentachlorobiphenyl (PCB 126), 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD), or an extract derived from field‐collected double‐crested cormorant eggs. These compounds were injected into the yolks of cormorant eggs from an isolated colony on Lake Winnipegosis, Manitoba, Canada. Upon hatching, chicks were necropsied. The brain, bursa, heart, liver, and spleen were removed and weighed. An approximate median lethal dose (LD50) of 158 μg/kg egg was determined for PCB 126, which is 69 times greater than the LD50 determined for the chicken (Gallus domesticus) in a previous study. A significantly greater mortality occurred at the highest dose of TCDD (4.0 μg/kg egg) when compared to the vehicle control. However, the mortality data did not provide sufficient information for the determination of an LD50. The cormorant egg extract did not adversely affect hatchability. No significant increases were observed in the incidence of developmental abnormalities, including pronounced edema, in any of the treatment groups, nor were there any relevant effects on body and organ weights. Based on the results from this study, the cormorant appears to be considerably less sensitive to polyhalogenated diaromatic hydrocarbons than the chicken, which has been the typical species used for egg injection studies.

Organochlorine Contaminants in Double-Crested Cormorants from Green Bay,Wisconsin: II. Effects of an Extract Derived from Cormorant Eggs onthe Chicken Embryo

White Leghorn chicken (Gallus domesticus) eggswere injected prior to incubation with one of four concentrations (0.001,0.01, 0.1, and 1.0 egg-equivalent) of an extract derived from 1,000double-crested cormorant (Phalacrocorax auritus) eggs collected atSpider Island adjacent to Green Bay in Lake Michigan. One egg-equivalentcorresponded to the concentration of contaminants present in an averagecormorant egg. This was approximately 322 pg toxic equivalents (TEQs)/g, wwegg with polychlorinatedbiphenyl congener 126(3,3',4,4',5-pentachlorobiphenyl) accounting for over 70% of the TEQs.Injection of 1.0 egg-equivalent resulted in 77% mortality at hatch.The incidence of developmental abnormalities (structural defects or edema)was not affected by injection of the extract. Body weight gain of chicks wasreduced in the 1.0 egg-equivalent dose group in the first, second, and thirdweek's post-hatch. Relative brain weights were greater and relativebursa weights were less in the 1.0 egg-equivalent dose group than in thevehicle control at three weeks of age. There were no significant differencesin the relative weights of the heart, liver, spleen, testes, or comb amongtreated and control birds.

Effects of 3,3',4,4'-tetrachlorobiphenyl, 2,3,3',4,4'-pentachlorobiphenyl, and 3,3',4,4',5-pentachlorobiphenyl on the developing chicken embryo when injected prior to incubation.

Great Lakes waterbird populations have experienced less-than-expected hatchability of eggs and a greater-than-expected incidence of developmental abnormalities. Such deleterious effects have been attributed to polyhalogenated hydrocarbons such as polychlorinated biphenyls (PCBs). PCBs are of primary concern since they are present in significant quantities in the environment. Specific PCB congeners, 3,3',4,4',5-pentachlorobiphenyl (IUPAC number 126), 3,3',4,4'-tetrachlorobiphenyl (IUPAC number 77), and 2,3,3',4,4'-pentachlorobiphenyl (IUPAC number 105), were injected (singly or in combination) into the yolks of White Leghorn chicken (Gallus domesticus) eggs prior to incubation. Teratogenicity was assessed in dead embryos and in hatchlings. Hatchlings were raised for 3 wk to assess body weight gain and mortality. At the end of the 3-wk period, chicks were subjected to necropsy and the brain, bursa, heart, liver, spleen, and testes were removed and weighed. All 3 congeners caused increased embryo mortality, with approximately 50% mortality occurring at 0.6, 8.8, and 5592 micrograms/kg egg for congeners 126, 77, and 105, respectively. All three congeners also produced significantly more abnormalities than the vehicle. Chicks from PCB-injected eggs had lower body weights at wk 2 and 3 of age. Congener 126 caused lower relative bursa weights, congener 77 caused greater relative spleen weights and lower relative liver weights, and all three congeners caused relative heart weights to be greater when compared to control.

Mutagen-induced fetal anomalies and death following treatment of females within hours after mating

In an earlier study (Generoso et al., 1987), it was observed that the mutagen, ethylene oxide (EtO), produced remarkable increases in the incidence of developmental abnormalities and death of fetuses when early zygotic stages were exposed. This is a major finding in experimental induction of embryopathy, implicating genetic damage to the zygotes as the likely cause. In the subsequent study reported here, 3 other mutagens — ethyl methanesulfonate (EMS), ethyl nitrosourea (ENU), and triethylene melamine (TEM), were studied for embryopathic effects following exposure of dictyate oocytes, prefertilization oviducal eggs and sperm, early pronuclear zygotes, zygotes undergoing pronuclear DNA synthesis, and two-cell embryos. All 4 mutagens produced developmental abnormalities among living fetuses following exposure of early pronuclear zygotes (the only stage studied for this endpoint in this report). With respect to stage specificity and gestational timing of death of conceptuses, EMS and EtO on one hand and ENU and TEM on the other, are very similar to one another. EMS, like EtO, produced a high incidence of midgestation and late fetal deaths only in prefertilization oviducal eggs and sperm and in early pronuclear eggs. In contrast, ENU and TEM produced high losses of conceptuses in all postmating stages studied but death occurred primarily prior to or around the time of implantation. Thus, the frequency of induction and the expression of embryopathy, which ranged from early embryonic preimplantation and late fetal deaths to subtle fetal anomalies, are dependent upon the stage exposed and the mutagen used.

Mutagen-induced fetal anomalies and death following treatment of females within hours after mating

In an earlier study (Generoso et al., 1987), it was observed that the mutagen, ethylene oxide (EtO), produced remarkable increases in the incidence of developmental abnormalities and death of fetuses when early zygotic stages were exposed. This is a major finding in experimental induction of embryopathy, implicating genetic damage to the zygotes as the likely cause. In the subsequent study reported here, 3 other mutagens — ethyl methanesulfonate (EMS), ethyl nitrosourea (ENU), and triethylene melamine (TEM), were studied for embryopathic effects following exposure of dictyate oocytes, prefertilization oviducal eggs and sperm, early pronuclear zygotes, zygotes undergoing pronuclear DNA synthesis, and two-cell embryos. All 4 mutagens produced developmental abnormalities among living fetuses following exposure of early pronuclear zygotes (the only stage studied for this endpoint in this report). With respect to stage specificity and gestational timing of death of conceptuses, EMS and EtO on one hand and ENU and TEM on the other, are very similar to one another. EMS, like EtO, produced a high incidence of midgestation and late fetal deaths only in prefertilization oviducal eggs and sperm and in early pronuclear eggs. In contrast, ENU and TEM produced high losses of conceptuses in all postmating stages studied but death occurred primarily prior to or around the time of implantation. Thus, the frequency of induction and the expression of embryopathy, which ranged from early embryonic preimplantation and late fetal deaths to subtle fetal anomalies, are dependent upon the stage exposed and the mutagen used.

Fish subchronic toxicity prediction model for industrial organic chemicals that produce narcosis

AbstractA model based on partition coefficient was developed for predicting subchronic toxicities of selected chemicals to fish. Early life stage tests were conducted under flow‐through conditions using fathead minnows (Pimephales promelas) as test organisms. Embryos, larvae and juveniles were continuously exposed to chemicals for a total of 31 to 33 d. Test endpoints included egg hatchability, incidence of developmental abnormalities, survival and growth. The “chronic value” for each test was a point estimate of the maximum acceptable toxicant concentration (MATC), and was determined as the geometric mean of the highest test concentration producing no effect and the lowest concentration significantly (p ≤ 0.05) affecting one or more endpoints. Ten industrial organic compounds from four chemical classes (ketones, benzenes, ethers and alkyl halides) were used in model development. All chemicals were considered to induce narcosis in fish in acute toxicity tests. The relationship between estimated MATC n‐octanol/water partition coefficient (log P) was expressed by the equationlog estimated MATC (mol L−1) = ‐0.886 log P ‐ 2.18 (r2 = 0.925).This model was used to predict subchronic toxicities for eight other alkyl halides and chlorinated benzenes that had been tested with fathead minnows and reported in the literature. The mean ratio for observed chronic toxicity value to predicted chronic toxicity value was 2.00 ± 2.03. Observed values ranged from 0.29 to 6.02 times the predicted values. For the 10 chemicals used in the model, the mean acute/chronic toxicity ratio (96‐h LC50/chronic value) was 12.2 ± 8.5.

Enzyme polymorphism, morphometric variation and population structure in a restricted endemic, Silene diclinis (Caryophyllaceae)

Silene diclinis is a dioecious perennial herb, restricted to a small area of the SE Spanish province of Valencia. Polyacrylamide gel electrophoresis and morphometric analysis were carried out on cultivated material derived from seed collected from the main population of S. diclinis at Játiva. Only two out of 26 inferred enzyme loci showed substantial variation. There was some indication of population subdivision in both. The esterase locus also showed homozygote excess within the population as a whole and within one subpopulation. Morphological characters showed significant differentiation between subpopulations. Low allozyme variability characterizes populations of most endemic species that have been investigated. Isolation and historical events may have been as important as population size or edaphic specialization in causing this low variability. But S. diclinis resembles other outbreeding plants in showing population structure and homozygote excess, suggesting restricted within-population gene flow. Mechanisms that may restrict gene flow in S. diclinis include environmentally-induced differences in flowering time, poor seed dispersal and possibly short pollinator foraging distances. Morphological variability and the incidence of developmental abnormalities are speculatively linked with homozygosity. Storage of genetic diversity in space can occur in restricted as well as widespread species and sampling for gene banking should then be spatially representative. Silene diclinis is threatened by continued habitat loss and consequent genetic erosion; its long-term future may depend on the gene bank and the botanic garden.

"Geographic" Variation in Sensitivity to X-Irradiation in Tribolium: II. Incidence of Developmental Abnormalities

Induction of developmental abnormalities was studied after x-irradiation of two-day-old pupae of various geographic populations of Tribolium castaneum and T. confusum. Canadian populations were the most sensitive; 21.1% showed the split wing abnormality in T. castaneum, and 37.5% showed this in T. confusum. Kenyan populations were the most resistant. They showed 1.0% abnormalities in T. castaneum and 16.7% in T. confusum. In general, T. castaneum was more resistant than T. confusum with 5.5% and 18.6% split wing abnormalities being produced, respectively. Length of the pupal stage was studied in T. castaneum. The pupal period decreased with increasing age at which larvae pupated. Emerged adults after irradiation had shorter pupal periods than their controls. This finding is contrary to earlier records, by other investigators, on eclosion delay using lower doses of x-irradiation and different pupal ages. Choice of dose, criteria, and consideration of the consequences of the choice of age at exposure are ...