Estrogen stimulated lipogenic activity in the ovary of the freshwater prawn,Macrobrachium Rosenbergü

Short-term exposure to benzo[a]pyrene disrupts reproductive endocrine status in the swimming crab Portunus trituberculatus

The purpose of this study was to investigate the effect of benzo[a]pyrene (B[a]P) on reproductive endocrine disruption and explore the preliminary mechanisms in crustaceans. In this study, sexually mature female Portunus trituberculatus were exposed to 0, 0.1, 0.5 and 2.5 μg/L B[a]P for 10 days. The following were investigated: (1) Gonadosomatic Index (GSI) and oocyte diameter, (2) steroid concentrations in ovary and hemolymph, and (3) mRNA levels of genes involved in sex steroid synthesis (3β-HSD,17β-HSD) or reproduction (estrogen receptor (ER), OUT (Ovarian tumor gene) domain containing ubiquitin aldehyde-binding protein 1 (OTUB1), vitellogenin (VTG),vasa). B[a]P exposure caused significant reductions in the GSI and oocyte diameter in the crabs. Furthermore, 17β-estradiol (E2), testosterone (T) and progesterone (P) levels were inhibited significantly while 3β-HSD and 17β-HSD mRNA expressions were also decreased in a dose-dependent manner at day 10, which suggests that B[a]P can disrupt sex steroid levels through steroid synthesis pathways. In addition, high levels of B[a]P activated transcription of OTUB1 while suppressed ER and VTG expression, which indicates that exposure to waterborne B[a]P could interfere with ubiquitin-proteasome pathway and subsequently affect ER and ER-mediated gene expression. We also observed a reduction in vasa gene expression reflecting the negative effect of B[a]P on oocyte development in the molecular level. This study is the first to demonstrate in vivo B[a]P toxicity in the reproductive endocrine system of female P. trituberculatus and provided a scientific basis of the decline in crustacean populations.

Hypothalamic gene switches control transitions between seasonal life history states in a night-migratory photoperiodic songbird

This study investigated photoperiodic plasticity in hypothalamic expression of genes implicated in the photoperiodic light perception (rhodopsin, melanopsin, neuropsin and peropsin), transduction (pax6, bmal1, clock, per2 and casr), induction (eya3, tshβ, dio2 and dio3, gnrh and gnih) and metabolism (NPY, sirtuin1, foxO1, hmgcr, citrate synthase and dehydrogenases) in photosensitive and photorefractory redheaded buntings. There was a significant increase in eya3, tsh β, dio2, pax6 and rhodopsin and decrease in dio3 mRNA expression at hour 15 and/or 19 on the day photosensitive buntings were subjected to a 13- or 16 h, but not to 8- and 11 h light exposure. Downstream reproductive and metabolic gene expression was not altered, except for an increase in those genes coding for succinate and malate dehydrogenase enzymes involved in lipogenesis. Photorefractory buntings had high dio3 mRNA expression which significantly declined after 1 short day exposure, suggesting possible involvement of dio3 in the maintenance of photorefractoriness. Positive correlation of rhodopsin on eya 3 and tshβ indicates its role in photoperiodic timing, perhaps involving the peropsin and pax6 genes. These results suggest that rapid switching of hypothalamic gene expression underlies photoperiod-induced seasonal plasticity and regulates transitions from photosensitive to photostimulated and from photorefractory to photosensitive states in migratory songbirds.

Reproductive regulators in decapod crustaceans: an overview

Control of reproductive development in crustaceans requires neuropeptides, ecdysone and methyl farnesoate (MF). A major source of neuropeptides is the X-organ-sinus gland (XO-SG) complex located in the eyestalk ganglia of crustaceans. The other regulatory factors (either peptides or neuromodulators) are produced in the brain and thoracic ganglia (TG). Two other regulatory non-peptide compounds, the steroid ecdysone and the sesquiterpene MF, are produced by the Y-organs and the mandibular organs, respectively. In the current review, I have tried to recapitulate recent studies on the role of gonadal regulatory factors in regulating crustacean reproduction.

Occurrence of vertebrate steroids, estradiol 17beta and progesterone in the reproducing females of the mud crab Scylla serrata

In crustaceans, vitellogenesis is known to be controlled by eyestalk neuropeptides, biogenic amines, ecdysteroids and a juvenile hormone-like compound, methyl farnesoate. In recent years, the occurrence of vertebrate steroid hormones, estradiol 17beta (E2) and progesterone (PG) has also been reported in a few decapods, although their precise role in female reproduction is yet to be determined. The levels of E2 and PG in the ovary, hepatopancreas and the hemolymph of the red mud crab, Scylla serrata were analyzed in different vitellogenic stages in order to establish a correlation between hormone profile and stages of vitellogenesis. It was observed that the levels of both the steroids increased steeply in the tissues at the onset of vitellogenesis (vitellogenic stage I). Maximum levels of estradiol were present in the hepatopancreas whereas the highest concentration of progesterone was seen in the ovary, suggesting dichotomous roles for these hormones in vitellogenesis. Furthermore, levels of these hormones were estimated in different embryonic stages of the eggs of the sand crab Emerita asiatica and mud crab S. serrata. Their levels fluctuated, following a definite pattern in the different stages, suggesting a possible functional role as morphogenetic hormones. This study, in addition, also reports the presence of E2 and PG on lipovitellin purified from ovary and eggs as well as vitellogenin purified from the hemolymph implicating a role for these lipoproteins as steroid carriers.

A parameter for detecting estrogenic exposure in the copepod Acartia tonsa

Literature on the basic endocrinology of crustaceans, such as crab, lobster and shrimp, suggest that estrogens, e.g., 17beta-estradiol, are stimulating hormones in female sexual maturation and egg production in crustaceans. The copepod Acartia tonsa, has continuous egg production. A profile of the egg production per time unit through the maturation of this species may be used as an expression of the degree of maturation of the female internal reproductive organs. Comparison of control profiles with profiles of estrogen-exposed copepods may thus demonstrate that estrogen exposure results in a steeper maturation profile. The proposed endpoint was identified by exposing copepods to the natural estrogen 17beta-estradiol and the antropogenic estrogen bisphenol A. Both compounds produced significant effects at 23 and 20 microg/L, respectively. Since bisphenol A is traditionally believed to be less estrogenic than 17beta-estradiol, the nonestrogen 2, 3-dichlorophenole was tested at 13.6 microg/L (molar concentration equal to 23 microg/L 17beta-estradiol) to test if the response is a general nonestrogenic toxic stress effect. The 2,3-dichlorophenole produced no effect.