Geology topics

Mara B. Bryan

Publications and source records attributed to Mara B. Bryan.

5 recordsLinked to original sources

USGS2013

Pheromonal bile acid 3-ketopetromyzonol sulfate primes the neuroendocrine system in sea lamprey

Background Vertebrate pheromones are known to prime the endocrine system, especially the hypothalamic-pituitary-gonadal (HPG) axis. However, no known pheromone molecule has been shown to modulate directly the synthesis or release of gonadotropin releasing hormone (GnRH), the main regulator of the HPG axis. We selected sea lamprey (Petromyzon marinus) as a model system to determine whether a single pheromone component alters the output of GnRH. Sea lamprey male sex pheromones contain a main component, 7α, 12α, 24-trihydroxy-5α-cholan-3-one 24-sulfate (3 keto-petromyzonol sulfate or 3kPZS), which has been shown to modulate behaviors of mature females. Through a series of experiments, we tested the hypothesis that 3kPZS modulates both synthesis and release of GnRH, and subsequently, HPG output in immature sea lamprey. Results The results showed that natural male pheromone mixtures induced differential steroid responses but facilitated sexual maturation in both sexes of immature animals (χ2 = 5.042, dF = 1, p < 0.05). Exposure to 3kPZS increased plasma 15α-hydroxyprogesterone (15α-P) concentrations (one-way ANOVA, p < 0.05) and brain gene expressions (genes examined: three lamprey (l) GnRH-I transcripts, lGnRH-III, Jun and Jun N-terminal kinase (JNK); one-way ANOVA, p < 0.05), but did not alter the number of GnRH neurons in the hypothalamus in immature animals. In addition, 3kPZS treatments increased lGnRH peptide concentrations in the forebrain and modulated their levels in plasma. Overall, 3kPZS modulation of HPG axis is more pronounced in immature males than in females. Conclusions We conclude that a single male pheromone component primes the HPG axis in immature sea lamprey in a sexually dimorphic manner.

BMC Neuroscience↗

USGS2013

An anti-steroidogenic inhibitory primer pheromone in male sea lamprey (Petromyzon marinus)

Reproductive functions can be modulated by both stimulatory and inhibitory primer pheromones released by conspecifics. Many stimulatory primer pheromones have been documented, but relatively few inhibitory primer pheromones have been reported in vertebrates. The sea lamprey male sex pheromone system presents an advantageous model to explore the stimulatory and inhibitory primer pheromone functions in vertebrates since several pheromone components have been identified. We hypothesized that a candidate sex pheromone component, 7α, 12α-dihydroxy-5α-cholan-3-one-24-oic acid (3 keto-allocholic acid or 3kACA), exerts priming effects through the hypothalamic-pituitary-gonadal (HPG) axis. To test this hypothesis, we measured the peptide concentrations and gene expressions of lamprey gonadotropin releasing hormones (lGnRH) and the HPG output in immature male sea lamprey exposed to waterborne 3kACA. Exposure to waterborne 3kACA altered neuronal activation markers such as jun and jun N-terminal kinase (JNK), and lGnRH mRNA levels in the brain. Waterborne 3kACA also increased lGnRH-III, but not lGnRH-I or -II, in the forebrain. In the plasma, 3kACA exposure decreased all three lGnRH peptide concentrations after 1 h exposure. After 2 h exposure, 3kACA increased lGnRHI and -III, but decreased lGnRH-II peptide concentrations in the plasma. Plasma lGnRH peptide concentrations showed differential phasic patterns. Group housing condition appeared to increase the averaged plasma lGnRH levels in male sea lamprey compared to isolated males. Interestingly, 15α-hydroxyprogesterone (15α-P) concentrations decreased after prolonged 3kACA exposure (at least 24 h). To our knowledge, this is the only known synthetic vertebrate pheromone component that inhibits steroidogenesis in males.

General and Comparative Endocrinology↗

USGS2013

A thermogenic secondary sexual character in male sea lamprey

Secondary sexual characters in animals are exaggerated ornaments or weapons for intrasexual competition. Unexpectedly, we found that a male secondary sexual character in sea lamprey (Petromyzon marinus ) is a thermogenic adipose tissue that instantly increases its heat production during sexual encounters. This secondary sexual character, developed in front of the anterior dorsal fin of mature males, is a swollen dorsal ridge known as the ‘rope’ tissue. It contains nerve bundles, multivacuolar adipocytes and interstitial cells packed with small lipid droplets and mitochondria with dense and highly organized cristae. The fatty acid composition of the rope tissue is rich in unsaturated fatty acids. The cytochrome c oxidase activity is high but the ATP concentration is very low in the mitochondria of the rope tissue compared with those of the gill and muscle tissues. The rope tissue temperature immediately rose up to 0.3°C when the male encountered a conspecific. Mature males generated more heat in the rope and muscle tissues when presented with a mature female than when presented with a male (paired t-test, P<0.05). On average, the rope generated 0.027±0.013 W cm -3 more heat than the muscle in 10 min. Transcriptome analyses revealed that genes involved in fat cell differentiation are upregulated whereas those involved in oxidative-phosphorylation-coupled ATP synthesis are downregulated in the rope tissue compared with the gill and muscle tissues. Sexually mature male sea lamprey possess the only known thermogenic secondary sexual character that shows differential heat generation toward individual conspecifics.

Journal of Experimental Biology↗

USGS2010

Annual sex steroid and other physiological profiles of Pacific lampreys ( Entosphenus tridentatus )

We documented changes in plasma levels of estradiol 17-β (E2), progesterone (P), 15α-hydroxytestosterone (15α-T), thyroxine (T4), triiodothyronine (T3), protein, triglycerides (TGs), and glucose in adult Pacific lampreys ( Entosphenus tridentatus ) held in the laboratory in two different years. Levels of E2 in both sexes ranged from 0.5 to 2 ng/mL from September to March, peaked in late April (2–4 ng/mL), and decreased in May, with levels higher in males than in females. Levels of P were low from September through April, but then increased substantially during May (2–4 ng/mL), with levels again highest in males. Levels of 15α-T in males were around 0.75 ng/mL through the winter before exceeding 1 ng/mL in April and decreasing thereafter, whereas females showed a gradual increase from 0.25 ng/mL in November to 0.5 ng/mL in April before decreasing. Thyroxine concentrations differed between fish in each year, with most having levels ranging from 0.75 to 2.5 ng/mL in the fall and winter, and only fish in 2003 showing distinct peaks (3–4 ng/mL) in early April or May. Plasma T3 was undetectable from November through mid-March before surging dramatically in April (ca. 150 ng/mL) and decreasing thereafter. Levels of protein, TGs, and glucose decreased or were stable during the fall and winter with TGs and glucose surging in late April to early May for some fish. Our study is the first to document long-term physiological changes in Pacific lampreys during overwintering and sexual maturation and increases our understanding of the life history of this unique fish.

Comparative Biochemistry and Physiology, Part A: M↗

USGS2006

Comparison of synthesis of 15α-hydroxylated steroids in males of four North American lamprey species

Recent studies have provided evidence that 15α-hydroxytestosterone (15α-T) and 15α-hydroxyprogesterone (15α-P) are produced in vitro and in vivo in adult male sea lampreys ( Petromyzon marinus ), and that circulatory levels increase in response to injections with gonadotropin-releasing hormone ( GnRH ). We examined four species from the Petromyzontidae family including silver lampreys ( Ichthyomyzon unicuspis ), chestnut lampreys ( I. castaneus ), American brook lampreys ( Lethenteron appendix ), and Pacific lampreys ( Entosphenus tridentatus ) to determine if these unusual steroids were unique to sea lampreys or a common feature in lamprey species. In vitro production was examined through incubations of testis with tritiated precursors, and 15α-T and 15α-P production was confirmed in all species through co-elution with standards on both high performance liquid chromatography ( HPLC ) and thin layer chromatography . In vivo production was proven by demonstrating that HPLC-fractionated plasma had peaks of immunoreactive 15α-T and 15α-P that co-eluted with standards through using previously developed radioimmunoassays for 15α-T and 15α-P. The possible functionality of 15α-T and 15α-P was further examined in silver and Pacific lampreys by investigating the effect of injection of either type of lamprey GnRH on plasma concentrations of 15α-T and 15α-P. Injections with exogenous GnRH did not affect circulatory levels of either steroid in silver lampreys, and only GnRH III elicited higher levels of both steroids in Pacific lampreys. The 15α-hydroxylase enzyme(s) for steroids appeared to present in adult males of all species examined, but the question of whether 15α-hydroxylated steroids are functional in these lamprey species, and the significance of the 15- hydroxyl group, requires further research.

General and Comparative Endocrinology↗