Vitellogenesis and aspects of its pituitary regulation in teleosts with emphasis on winter flounder (Pseudopleuronectes americanus)

The ovarian uptake of the homologous serum proteins vitellogenin (VG) and very high density lipoprotein II (VHDL II) (formerly peak A protein) were studied as potential yolk precursors involved in vitellogenesis in winter flounder (Pseudopleuronectes americanus). The major yolk precursor appears to be VG based on the quantity of yolk protein that recognizes the VG and VHDL II antisera by Western blotting. The rate of uptake of VG by the ovary is about three times greater than VHDL II. Internalized VG is processed into a 280,000 relative molecular mass (Mr) yolk protein (lipovitellin) that contributes to the major fraction (82%) of ovarian protein. Accumulation of VHDL II occurs in an unprocessed form and contributes to a fraction of ovarian protein representing 12% of the total. Phosvitin and a low Mr phosphoprotein were apparent but in small amounts. -- In vitro ovarian incubations done during the prespawning to early vitellogenic phases of the reproductive cycle in winter flounder showed that pituitary extract stimulates estradiol-17β (E₂) production only during the vitellogenic phase, while induced testosterone (T) production was greatest shortly before spawning. These observations were reflected in the seasonal pattern of serum levels of E₂ and T in female winter flounder. To investigate the effect of sockeye salmon carbohydrate-poor (Con A I) and carbohydrate- rich (Con A II) pituitary protein fractions on E₂ production,, ovarian follicles with (intact) or without the surface epithelium-thecal cell layer (defolliculated) from rainbow trout (Qncorhvnchus mykiss) were incubated in vitro. It was demonstrated that Con A I in the presence of T is capable of significantly increasing E₂ production in defolliculated ovarian follicles while under similar conditions Con A II (containing the maturational gonadotropin) was not. Purified salmonid and pleuronectid growth hormones (GHs) were tested for their ability to increase either E₂ and T production during in vitro ovarian incubations in both rainbow trout and winter flounder respectively, but were found to be inactive. -- Growth hormones were isolated from the pituitaries of sockeye salmon (Qncorhvnchus nerka) and American plaice (Hippoglossoides platessoides). A bioassay based on the increase of serum triiodothyronine in rainbow trout was developed to follow GH biological activity during pituitary fractionation. The isolation of a pituitary protein from sockeye salmon that was active in the bioassay was confirmed as monomeric GH by an amino-terminal (N-T) amino acid sequence. In plaice GH variants were isolated from two Mr regions within the pituitary, 42,000 and <33,000, that were active in the bioassay and had identical N-T amino acid sequences. The 42,000 Mr form predominates in the plaice pituitary making up 93% of the total

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Variation Among Rainbow Trout (Oncorhynchus mykiss) Estrogen Receptor Isoform 3′ Untranslated Regions and the Effect of 17β-Estradiol on mRNA Stability in Hepatocyte Culture

Adenine and uridine (AU)–rich elements in the 3′ untranslated region (3′UTR) have been implicated in the 17β-estradiol (E2) stabilization of vertebrate estrogen receptor (ER) mRNAs. To date, fishes have the most complex arrangement of nuclear ERs with up to two isoforms of each of the two genes in some species (i.e., four different ERs). The objective of this study was to analyze the sequence variation of 3′UTRs among the four ER isoforms in the rainbow trout and determine to what degree it is responsible for the estrogen-induced increase of ER mRNAs in the liver of this fish. This was done by comparing the 3′UTR DNA sequence length and composition, and by measuring expression of ER isoform 3′UTR luciferase reporter constructs in primary cultures of trout hepatocytes treated with E2. There were large differences both in overall length and in sequence composition among the four ER isoform 3′UTRs. The ERα1 sequence was the longest and the only one of the four that contained multiple copies of the canonical AU-rich elements (AUUUA) as well as the stability sequence (GCUGAU). E2 treatment significantly increased the luciferase activity in cells transiently transfected with the ERα1 reporter construct, relative to cells transfected with reporter vectors containing the other three ER isoform 3′UTRs or the parental vector control. These results support the hypothesis that the E2-induced increase in hepatic ERα1 mRNA in rainbow trout is due in part to sequence variability among ER isoform 3′UTRs. We conclude that posttranscriptional stabilization of ER mRNA by E2 appears to be conserved among vertebrates

Estrogen receptor mRNA expression patterns in the liver and ovary of female rainbow trout over a complete reproductive cycle

► Estrogen receptor gene expression quantified in female rainbow trout. ► Estrogen receptor alpha 1 was highest in the liver. ► Ovary estrogen receptor alpha 2 peaked toward the end of the reproductive cycle. ► Estrogen receptor beta levels were high at the onset of a new cycle then decreased. Estrogens are critical hormones involved in reproduction and need to bind to estrogen receptors in target organs for biological activity. Fishes have two distinct estrogen receptor subtypes, alpha (α) and beta (β), with variable combinations of additional isoforms of each subtype dependent on the history of genome duplication within a taxon. The comparative expression patterns of estrogen receptor isoforms during the female reproductive cycle will provide important insights into the unique function and importance of each. The purpose of this study was to measure the mRNAs for the four estrogen receptor isoforms (erα1, erα2, erβ1, erβ2) in the liver and ovary of adult, female rainbow trout over the course of an annual reproductive cycle. The expression of estrogen receptor mRNA isoforms was measured by quantitative real-time RT-PCR. Several reproductive indices (gonadosomatic index, maximum oocyte diameter, plasma estradiol-17β, plasma vitellogenin, and ovulation) were also quantified for comparison and used in a correlation analysis to examine any inter-relationships. Of the four isoforms, the expression of erα1 was highest in the liver, and had a significant positive correlation with liver erβ1 expression. Liver expression of erα2 mRNA was the lowest, but showed a significant positive correlation with maximum oocyte diameter in the ovary. The pattern of the erβ isoforms in liver was one of initially elevated mRNA expression followed by a gradual decrease as reproductive development proceeded. In the ovary the erβ1 isoform had the highest mRNA expression of all estrogen receptor isoforms, at the beginning of the reproductive cycle, but then decreased afterward. Both ovarian erβ isoforms had a significant positive correlation with one another. In contrast, erα2 mRNA expression showed a high maximum level in the ovary near the end of the cycle along with a significant positive correlation with plasma estradiol-17β levels; the highest gonadosomatic indices, maximum oocyte diameter, and vitellogenin levels occurred then too

MODELING THE ENDOCRINE CONTROL OF VITELLOGENIN PRODUCTION IN FEMALE RAINBOW TROUT

The rainbow trout endocrine system is sensitive to changes in annual day length, which is likely the principal environmental cue controlling its reproductive cycle. This study focuses on the endocrine regulation of vitellogenin (Vg) protein synthesis, which is the major egg yolk precursor in this fish species. We present a model of Vg production in female rainbow trout which incorporates a biological pathway beginning with sex steroid estradiol-17β levels in the plasma and concluding with Vg secretion by the liver and sequestration in the oocytes. Numerical simulation results based on this model are compared with experimental data for estrogen receptor mRNA, Vg mRNA, and Vg in the plasma from female rainbow trout over a normal annual reproductive cycle. We also analyze the response of the model to parameter changes. The model is subsequently tested against experimental data from female trout under a compressed photoperiod regime. Comparison of numerical and experimental results suggests the possibility of a time-dependent change in oocyte Vg uptake rate. This model is part of a larger effort that is developing a mathematical description of the endocrine control of reproduction in female rainbow trout. We anticipate that these mathematical and computational models will play an important role in future regulatory toxicity assessments and in the prediction of ecological risk

Estrogen receptor mRNA expression patterns in the liver and ovary of female rainbow trout over a complete reproductive cycle

Estrogens are critical hormones involved in reproduction and need to bind to estrogen receptors in target organs for biological activity. Fishes have two distinct estrogen receptor subtypes, alpha (α) and beta (β), with variable combinations of additional isoforms of each subtype dependent on the history of genome duplication within a taxon. The comparative expression patterns of estrogen receptor isoforms during the female reproductive cycle will provide important insights into the unique function and importance of each. The purpose of this study was to measure the mRNAs for the four estrogen receptor isoforms (erα1, erα2, erβ1, erβ2) in the liver and ovary of adult, female rainbow trout over the course of an annual reproductive cycle. The expression of estrogen receptor mRNA isoforms was measured by quantitative real-time RT-PCR. Several reproductive indices (gonadosomatic index, maximum oocyte diameter, plasma estradiol-17β, plasma vitellogenin, and ovulation) were also quantified for comparison and used in a correlation analysis to examine any inter-relationships. Of the four isoforms, the expression of erα1 was highest in the liver, and had a significant positive correlation with liver erβ1 expression. Liver expression of erα2 mRNA was the lowest, but showed a significant positive correlation with maximum oocyte diameter in the ovary. The pattern of the erβ isoforms in liver was one of initially elevated mRNA expression followed by a gradual decrease as reproductive development proceeded. In the ovary the erβ1 isoform had the highest mRNA expression of all estrogen receptor isoforms, at the beginning of the reproductive cycle, but then decreased afterward. Both ovarian erβ isoforms had a significant positive correlation with one another. In contrast, erα2 mRNA expression showed a high maximum level in the ovary near the end of the cycle along with a significant positive correlation with plasma estradiol-17β levels; the highest gonadosomatic indices, maximum oocyte diameter, and vitellogenin levels occurred then too

Reproductive development in captive reconditioned female steelhead kelts: evidence for consecutive and skip spawning life histories

Reconditioning of post-spawned anadromous rainbow trout (steelhead kelts, Oncorhynchus mykiss) is being implemented as a recovery tool on the Yakima River in the mid-Columbia River Basin. We assessed reproductive development in female Yakima River kelts by measuring plasma estradiol-17β (E2) and vitellogenin (VG) levels during reconditioning in 2009–2011. Plasma E2 and VG levels showed that fish separated into rematuring (consecutive spawning) and nonrematuring (presumed skip spawning) cohorts by October. Rematuration rates varied from 25% to 65%. Rematuring fish were consistently detected migrating toward spawning areas after release, whereas nonrematuring fish were occasionally detected on spawning migrations the following year. Rematuring fish grew more rapidly than nonrematuring fish over the reconditioning period and had higher muscle lipid levels and condition factor in October. Plasma E2 was elevated in rematuring fish by June–July, whereas plasma VG was elevated by June–August, suggesting that maturation decisions occur early in reconditioning. Rematuring and nonrematuring females could be separated by plasma E2 and VG levels by August–September, enabling separate management of consecutive and presumed skip spawners