Congress Abstracts - Society for Developmental Biology

Program/Abstract # 573
Fluoride induces apoptosis in Sertoli cells in vitro
Erkan, Melike (Istanbul Univ, Turkey)
Fluorine is potent toxicant, widely distributed through drinking water and food. Fluorine is not freely found in nature, it combines with
almost all metals and nonmetals, except oxygen and the noble gases. Fluoride is found in drinking water and foods threat to the
environment and human health. Although several hypotheses have been proposed, the exact mechanism of fluoride has not been
clearly defined. Fluoride accumulation leads to a large number of hematological, hepatic, renal and neurological disorders. Although
research has been carried out on the effects of fluoride on the reproductive organs and reproductive system impairment in animal
models, the results are controversial. Increasing exposure of fluorides on daily basis might have a potential negative impact on male
fertility, including spermatogenesis and sperm fertilizing ability. However, the effects of fluoride on reproductive organs are not fully
understood. The present study was aimed at determining the direct effects of sodium fluoride on Sertoli cell viability, proliferation,
cytotoxicity and apoptosis/necrosis rate in vitro. In this study, sodium fluoride was exposed to TM4 Sertoli cells for 24, 48 and 72
hours at 2 ppm and 16 ppm doses. After incubation, the treated cells were used for measurement of cell viability, proliferation, lactate
dehydrogenase assay and propidium iodide and Hoechst stain for apoptosis/necrosis rate. The results indicated that cell viability and
cell proliferation are decreased, while lactate dehydrogenase levels and apoptosis/necrosis rate are increased. These findings suggest
that direct exposure to fluoride could induce cytotoxicity and resulting in the apoptosis of Sertoli cells.
Program/Abstract # 574
Telomere biology in the switching of reproductive modes in planarian Dugesia ryukyuensis
Nodono, Hanae (Keio Univ, Japan); Aboobaker, Aziz (Oxford, UK); Matsumoto, Midori (Keio Univ, Japan)
Eukaryotic chromosomes get shorter as cells divide and cells senesce when telomeres shorten to a critical length, which is
hypothesized to be a contributory factor to ageing and mortality in sexually reproducing organisms. However, some eukaryotes can
reproduce both sexually and asexually. It is unclear whether reproductive mode and ageing correlates or not. To ask this question, we
focus on freshwater planarians. They reproduce either asexually, by fission, or sexually, by cross-fertilization. Several planarians use
exclusively one mode of reproduction; others might alternate between them. Schmidtea mediterranea is one of the former species,
comprised of obligate asexuals and sexuals. Recently, it was showed that asexuals recover age-related telomere shortening through
fission, whereas sexual worms only achieve telomere elongation through sexual reproduction. This difference correlated with the
expression level of an active spliceform of the telomere reverse transcriptase subunit (Smed-tert). Our model species Dugesia
ryukyuensis is comprised of populations with different reproductive strategies: exclusively innately asexual, exclusively innately
sexual, and seasonally switching. Moreover asexuals can be sexualized by feeding them with minced sexuals. In this report, we
compared telomere biology of these strains. In contrast to S. mediterranea, D. ryukyuensis sexual worms showed a slight telomere
shortening. Then a tert homolog (Dr-tert) was identified and characterized. Though two alternate splice sites were identified like
Smed-tert, all strains expressed high-level of active isoform, which correlated with their telomere length dynamics and telomerase
activity. These results suggest the existence of immortal sexually reproducing animals that can maintain their telomere length.
Program/Abstract # 575
Effect of maternal glucocorticoid exposure on mouse embryonic development
Lee, Ji-Yeon Lee; Yun, Hyo Jung; Kim, Jongsoo; Kim, Myoung Hee (Yonsei Univ Coll of Med, Rep of Korea)
Prenatal stress is known to cause intrauterine growth retardation and physiological dysfunctions in various aspects. In addition, many
of the diseases associated with prenatal stress exhibit a sex bias. Perturbations and vulnerability to prenatal stress are often more
profound for the male fetus, however, the mechanisms responsible for this relationship are not clear. We previously have shown that
administration of dexamethasone at gestational day 7.5~9.5, a critical time point on early placenta development, induces placental
defects as well as embryonic growth restriction. In the present study, we further examined the dexamethasone-induced morphological
changes during fetal growth and investigated the influence of prenatal glucocorticoid exposure on sex-specific gene expression and
male gonad development. Compared with the control group, 30% of the experimental group exhibited homeotic transformation and
other alterations of the axial skeleton. Moreover, embryos exposed to dexamethasone showed smaller rib cages and varying degrees of
xiphoid process protrusion. Here we will present these skeletal malformations and morphological development of the testes in male
mouse fetuses treated in utero with dexamethasone.
Program/Abstract # 576
The Effect of Methylmercury on Neural Gene Expression in Zebra Finch Development
Murray, Jessica R.; Ramos, Claire; Cristol, Dan; Saha, Margaret (College of William and Mary, USA)
Mercury is a highly toxic pollutant that adversely affects neural development. Preliminary data reveal that male juvenile zebra finch
(Taeniopygia guttata) learn a less complex and lower pitched song after developmental exposure to methylmercury. Zebra Finches are
the most commonly used laboratory songbird species, yet their embryological development has been poorly characterized. Most
studies to date apply Hamburger and Hamilton stages derived from chicken development, however significant differences exist
between development of the two species. Here we provide the first detailed description of embryological development in zebra finch
under standard artificial incubation. Once the embryology was characterized, expression of key song learning genes (e.g., FoxP2) in
Zebra Finch embryos whose parents had been raised on a diet containing low, biologically relevant levels of mercury was
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