Sirinart Techa | University of Maryland (original) (raw)

Papers by Sirinart Techa

<p>The data are presented as mean ± SE. Native CasMIH for RIA standards was prepared as des... more <p>The data are presented as mean ± SE. Native CasMIH for RIA standards was prepared as described [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117278#pone.0117278.ref075" target="_blank">75</a>]. All data were subjected to a normality test using the Shapiro-Wilk test (SigmaPlot). Statistical significance was accepted at <i>P</i> < 0.05 and noted with letters.</p

Title of dissertation: The functional importance and significance of ecdysteroids in molt-cycle r... more Title of dissertation: The functional importance and significance of ecdysteroids in molt-cycle regulation of the blue crab, Callinectes sapidus Sirinart Techa, Doctorate of Philosophy, 2014 Dissertation directed by Associate Professor J. Sook Chung Marine Estuarine Environmental Science This study aims to expand our understanding of how ecdysteroids and neuropeptide hormones (MIH/CHH) regulate molting in crustaceans using the blue crab Callinectes sapidus as a model animal. The hypothesis of this study is that ecdysteroids have a stimulatory effect on MIH/CHH production in eyestalks while generating both positive and negative feedback on ecdysteroidogenesis in Y-organs. Since ecdysteroids exert their signals through an ecdysteroid receptor complex, composed of an ecdysone receptor (EcR) and its partner, the retinoid-X receptor (RXR), the functional activity of ecdysteroids on tissues of interest is examined through EcR expression. Endogenous levels of ecdysteroids as well as expres...

Title of thesis: ECDYSONE AND RETINOID-X RECEPTORS OF THE BLUE CRAB, CALLINECTES SAPIDUS: CLONING... more Title of thesis: ECDYSONE AND RETINOID-X RECEPTORS OF THE BLUE CRAB, CALLINECTES SAPIDUS: CLONING AND TEMPORAL EXPRESSION IN EYESTALK GANGLIA AND Y-ORGANS DURING THE MOLT CYCLE Sirinart Techa Master of Science, 2012 Thesis directed by Associate Professor J. Sook Chung Marine Estuarine Environmental Science The molt cycle in decapod crustaceans, including the blue crab, Callinectes sapidus, is supressed by the crustacean hyperglycemic hormone (CHH) neuropeptide family and stimulated by ecdysteroids (Ecds). The Ecds are thought to act on both eyestalk ganglia (ES) and Y-organs (YO) where the CHH neuropeptides and Ecds are synthesized, respectively. Since the resultant responses of Ecds are mediated through their nuclear receptors: ecdysone receptor (EcR) and retinoid-X receptor (RXR), the temporal expression of EcR-RXR in ES and YO during the molt cycle may reveal the regulatory role of Ecd on the activity of these two organs. In this study, the full-legnth cDNA sequences of C. sapidu...

Arthropod molt is coordinated through the interplay between ecdysteroids and neuropeptide hormone... more Arthropod molt is coordinated through the interplay between ecdysteroids and neuropeptide hormones. In crustaceans, changes in the activity of Y-organs during the molt cycle have been regulated by molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH). Little has been known of the mode of direct effects of ecdysteroids on the levels of MIH and CHH in the eyestalk ganglia during the molt cycle. This study focused on a putative feedback of ecdysteroids on the expression levels of MIH transcripts using in vitro incubation study with ecdysteroids and in vivo RNAi in the blue crab, Callinectes sapidus. Our results show a specific expression of ecdysone receptor (EcR) in which EcR1 is the major isoform in eyestalk ganglia. The initial elevation of MIH expression at the early premolt stages is replicated by in vitro incubations of eyestalk ganglia with ecdysteroids that mimic the intrinsic conditions of D 0 stage: the concentration (75 ng/ml) and composition (ponasterone A and 20-hydroxyecdysone at a 3:1 (w:w) ratio). Additionally, multiple injections of EcR1-dsRNA reduce MIH expression by 67%, compared to the controls. Our data provide evidence on a putative feedback mechanism of hormonal regulation during molting cycle, specifically how the molt cycle is repeated during the life cycle of crustaceans. The elevated concentrations of ecdysteroids at early premolt stage may act positively on the levels of MIH expression in the eyestalk ganglia. Subsequently, the increased MIH titers in the hemolymph at postmolt would inhibit the synthesis and release of ecdysteroids by Y-organs, resulting in re-setting the subsequent molt cycle.

Crustacean molting is known to be regulated largely by ecdysteroids and crustacean hyperglycemic ... more Crustacean molting is known to be regulated largely by ecdysteroids and crustacean hyperglycemic hormone (CHH) neuropeptide family including molt-inhibiting hormone (MIH) and CHH. The surge of 20-OH ecdysone and/or ponasterone A initiates the molting process through binding to its conserved heterodimeric nuclear receptor: Ecdysone Receptor (EcR) and Ultraspiracle (USP)/Retinoid-X Receptor (RXR). To better understand the role of ecdysteroids in the molt regulation, the full-length cDNAs of the blue crab, Callinectes sapidus EcR1 and RXR1 were isolated from the Y-organs and their expression levels were determined in both Y-organs and eyestalks at various molt stages. Y-organs show the expression of four putative isoforms of CasEcRs and CasRXRs which differ in the length of the open reading frame but share the same domain structures as in typical nuclear receptors: AF1, DBD, HR, LBD, and AF2. The putative CasEcR isoforms are derived from a 27-aa insert in the HR and a 49-aa residue substitution in the LBD. In contrast, an insertion of a 5-aa and/or a 45-aa in the DBD and LBD gives rise to CasRXR isoforms. The eyestalks and Y-organs show the co-expression of CasEcRs and CasRXRs but at the different levels. In the eyestalks, the expression levels of CasRXRs are 3-5 times higher than those of CasEcRs, while in Y-organs, CasRXRs are 2.5-4 times higher than CasEcRs. A tissue-specific response to the changes in the levels of hemolymphatic ecdysteroids indicates that these tissues may have differences in the sensitivity or responsiveness to ecdysteroids. The presence of upstream open reading frame and internal ribosome entry site in 5&amp;amp;amp;amp;amp;#39; UTR sequences of C. sapidus and other arthropod EcR/RXR/USP analyzed by in silico indicates a plausible, strong control(s) of the translation of these receptors.

General and Comparative Endocrinology

Embryogenesis requires the involvement and coordination of multiple networks of various genes, ac... more Embryogenesis requires the involvement and coordination of multiple networks of various genes, according to a timeline governing development. Crustacean embryogenesis usually includes the first molt, a process that is known to be positively controlled by ecdysteroids. We determined the amounts of ecdysteroids, as well as other related factors: the ecdysone receptor (CasEcR), the retinoid X receptor (CasRXR), the molt-inhibiting hormone (CasMIH), and crustacean hyperglycemic hormone (CasCHH) during the ovarian and embryonic developments of Callinectes sapidus. In summary, the ovaries at stages 1-4 have expression levels of maternal CasEcR and CasRXR 10-50 times higher than levels seen in embryos at the yolk stage. This large difference in the amount of the these factors in C. sapidus ovaries suggests that these maternal ecdysteroid-responsive factors may be utilized at the initiation of embryogenesis. During embryogenesis, the changes in total ecdysteroids and levels of CasEcR and Ca...

General and Comparative Endocrinology