Investigation of the Superlattice Phases Formed in TaRu.

The Ta-Ru binary phase diagram has not been fully investigated, but shows potential for a two-phase region of A2 + B2. Given the high melting points of both Ta and Ru, such an alloy would have the potential for high temperature strength. A TaRu alloy was arc melted and investigated in the as-cast and aged (at 1000 °C) states.

Dose-response relationship of 15alpha-hydroxylated sex steroids to gonadotropin-releasing hormones and pituitary extract in male sea lampreys (Petromyzon marinus).

The sea lamprey (Petromyzon marinus) is one of the earliest extant vertebrates for which the hypothalamic-pituitary-gonadal (HPG) axis has been shown to control and regulate reproduction in a similar fashion to gnathostome vertebrates. While the two forms of gonadotropin-releasing hormones in the sea lamprey (GnRH I and GnRH III) have been studied extensively, their in vivo effect on synthesis of 15alpha-hydroxytestosterone (15alpha-T) and 15alpha-hydroxyprogesterone (15alpha-P) have only been partially characterized. In the present study, plasma concentrations of 15alpha-T and 15alpha-P were measured in prespermiating sea lampreys that were given a single injection of either GnRH I or GnRH III in doses ranging from 5 to 100 microg/kg, or of pituitary extract (as a source of gonadotropin).

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

Recent studies have provided evidence that 15 alpha-hydroxytestosterone (15 alpha-T) and 15 alpha-hydroxyprogesterone (15 alpha-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.

15Alpha-hydroxyprogesterone in male sea lampreys, Petromyzon marinus L.

There is growing evidence that sea lampreys, Petromyzon marinus L., produce gonadal steroids differing from those of other vertebrates by possessing an additional hydroxyl group at the C15 position. Here we demonstrate that sea lamprey testes produce 15alpha-hydroxyprogesterone (15alpha-P) in vitro when incubated with tritiated progesterone, that 15alpha-P is present in the plasma of sea lampreys, and that plasma concentrations of immunoreactive (ir) 15alpha-P rise dramatically in response to injections of gonadotropin-releasing hormone (GnRH).

15alpha-hydroxytestosterone induction by GnRH I and GnRH III in Atlantic and Great Lakes sea lamprey (Petromyzon marinus L.).

The sea lamprey (Petromyzon marinus L.) represents one of the two most ancient classes of vertebrates and possesses a functional hypothalamus-pituitary-gonadal axis. However, the presence and functionality of androgens in the sea lamprey remain elusive.