Research

Research Projects

The research interests and current projects we pursue in my lab are as follows:

Endocrine Control of Early Oogenesis in Salmonid Fishes
Supported by the USDA-CSREES NRI

Understanding the control of the development of oocytes into fertilizable eggs is necessary to overcome some of the reproductive problems that occur both in commercial aquaculture and in culture of endangered species in captive broodstock programs. Little is known about the early phases of oocyte development, despite the fact that this is when fecundity is largely determined. The purpose of this project is to understand the hormonal mechanisms controlling the critical early events in the development of oocytes of fishes that lead to the production of primary oocytes which can be recruited into the growth pathway and accumulate yolk. The project is focussing on the role of pituitary follicle-stimulating hormone, sex steroids, and insulin-like growth factor I in regulating the early stages of oogenesis in rainbow trout, including proliferation of oogonia, their entry into meiosis and growth of the resulting primary oocytes. We are utilizing in vitro techniques together with developing the unilaterally ovariectomized trout as a model, since ovariectomy results in compensatory recruitment and growth in the remaining ovary. Collaborators include Dr. Penny Swanson (Northwest Fisheries Science Center, Seattle) and Dr. Briony Campbell, University of Washington), and Dr. Takeshi and Chiemi Miura (Ehime University, Japan).

Endocrine Control of the Onset of Spermatogenesis in Salmonid Fish
Postdoctoral researcher supported by the Japan Society for the Promotion of Science

Work from Dr. Penny Swanson's group (NOAA Fisheries, Northwest Fisheries Science Center, Seattle) suggests that onset of puberty in male Pacific salmon depends on growth rate at certain critical periods that may be a year or more before spawning can potentially take place. How growth rate is translated into chemical cues that trigger the beginning of sperm cell development is not completely clear, but attention has focussed on hormones of the growth axis, particularly insulin-like growth factor I, and the likely direct initiator of spermatogenesis, follicle stimulating hormone. Using both in vivo and in vitro techniques, we aim to describe the molecular and cellular events occurring prior to and during the onset of androgen production in a model species, rainbow trout, and to take an in vitro experimental approach to determine the roles of various factors in controlling this process. We are also collaborating with Dr. Swanson in her Bonneville Power Administration-funded projects examining the mechanisms whereby growth affects puberty in Pacific salmon.

Effects of Endogenous Steroids and Environmental Contaminants on Reproduction
Partially supported by the USDA-CSREES NRI program

Many environmental contaminants, termed environmental endocrine disrupters (EEDs), have deleterious, sub-lethal effects on vertebrate animals. Development, reproduction and growth are often impaired, and in many cases, this has been associated with the disruption of the endocrine systems controlling these processes, and linked to the steroid hormone-like actions of EEDs. Many EEDs bind to nuclear steroid hormone receptors, proteins that modulate the transcription of target genes following hormone binding. These EEDs may either activate nuclear receptors and hence gene transcription, or may block the binding of the naturally occurring ligand. Examples of effects of EEDs (e.g., alkylphenolic chemicals, plasticizers, phthalates, pesticides and herbicides) on fish include induction of yolk protein synthesis by liver of male fish, male to female sex reversal, and depression of hormones. Effects of EEDs on the levels of reproductive hormones such as pituitary gonadotropins and steroids produced in the gonads (sex steroid hormones) or interrenal (corticosteroids) may be in part due to their feedback actions on the brain and pituitary to suppress release of tropic hormones that regulate steroid production but we have now have evidence that steroid-producing tissues are direct targets for EEDs. We are pursuing two lines of research. First, using the molecular tools we have recently developed, we are determining the effects of endogenous steroids and EEDs on steroidogenic proteins. Second, as part of a larger collaborative effort led by Dr. Penny Swanson (Northwest Fisheries Science Center, Seattle), we are assessing the effects of environmentally realistic concentrations of EEDs on a number of elements of the endocrine and reproductive systems. Other collaborators include Dr Irvin Schultz and Ann Skillman (Pacific Northwest National Laboratory) and Jim Nagler (University of Idaho).

Physiological Markers in Salmonid Peritoneal Fluid Composition
Supported by Digital Angel Corporation

This study represents the initial exploratory research phase of a project that is focused on developing an enhanced passive integrated transponder (PIT) tag capable of passively measuring and reporting changes in the physiological state of a fish using the installed Columbia River Basin (CRB) PIT tag system infrastructure. The PIT tag is currently used only for fish identification and tracking in the CRB. It is normally implanted in the peritoneal cavity of fish and thus in contact with peritoneal fluid and gas. We hypothesize that changes to the peritoneal fluid and gas within the cavity occur when a fish is subjected to environmental change. Some of the parameters that undergo change may reflect changes occurring in the blood of fish subject to stress and thus may be used as biomarkers for stress. It may be possible to detect changes in one or more peritoneal fluid parameters using nanosensors incorporated into an enhanced PIT tag. Questions regarding the magnitude of stress imposed on fish migrating through the various passageways of a hydroelectric dam may be addressed using this tool. In addition, availability of an enhanced PIT tag would facilitate non-destructive sampling in laboratory studies addressing inquiries into smoltification, reproduction and environmental physiology. This work is based at the University of Idaho, in collaboration with Dr Rolf Ingermann and his graduate student, Micah Zuccarelli.

Eel Migration and Reproduction
Work continuing in New Zealand, initiated and led by Dr Mark Lokman, University of Otago

Aquaculture of freshwater eels is a major industry in Southeast Asia and Europe. However, this industry is totally reliant on the supply of juvenile glass eels from the wild because breeding in captivity has never been routinely accomplished. Adult eels migrate from fresh water to their oceanic spawning grounds at a very early stage of gonadal development. The reproductive system of adult eels shuts down completely upon capture. Mature gametes can be obtained after prolonged treatment with gonadotropin preparations but the resulting larvae are often short-lived. Until recently, very little was known about the reproductive physiology of naturally maturing eels. Long-finned New Zealand eels are unique in that they migrate to the ocean at a time when their oocytes are mid-vitellogenic, and testes are mid-spermatogenic. Thus, former PhD student (now on faculty at the University of Otago) Mark Lokman was able to study reproductive events in naturally maturing eels for the first time. In collaboration with Japanese colleagues we have used this information to assess whether artificial maturation protocols effectively mimic the changes observed in the wild, and our results suggest aberrant yolking of oocytes of gonadotropin-treated eels. Furthermore, studies on two species of New Zealand eels revealed a puzzling phenomenon: high levels of the male specific androgen, 11-ketotestosterone (11-KT), in migrating female eels. Anguillid eels provide a textbook example of semelparous catadromy, a life history trait that requires many developmental adaptations to occur (metamorphosis) coincident with the initiation of puberty (e.g., increased eye size, increased countershading, and changes in muscle). Recent work has shown that implantation of 11-KT in immature eels can induce physiological and morphological changes normally associated with the adult metamorphosis:11-KT may function as a general metamorphic hormone, a unique action for an androgen.

Salmon Parr–Smolt Transformation

The transformation of the freshwater juvenile salmon parr into seaward migrating smolts involves coordinated changes in physiology, behavior, biochemistry and morphology, all of which are driven by the endocrine system. Ultimately, these changes permit these animals to successfully adapt to the osmoregulatory challenge of moving from a hypoosmotic to a hyperosmotic environment. Inappropriate timing of entry into seawater (for example, in sea cage transfers) results in death or growth retardation (stunting). My past involvement in research in this area includes documenting changes in a number of hormones, some for the first time, during the parr-smolt transformation, analyzing the endocrine correlates of stunting, demonstrating effects of cortisol and growth hormone on gill Na, K-ATPase, and insulin-like growth factor 1 on growth, and developing a radioreceptor assay for growth hormone receptors. Although the regulation of gill Na, K-ATPase is now well understood, a large gap in our knowledge concerns how ion and water absorption by the intestine are regulated by smolt-related hormones. Dr Philip Veillette, my former PhD student at the University of Otago and now at the University of Rhode Island, developed an in vitro culture system to study the hormonal regulation of Na, K-ATPase in the pyloric caeca and intestine. Phil was able to demonstrate direct effects of cortisol on pyloric caeca and intestine Na, K-ATPase activity, and showed that pyloric caeca are major osmoregulatory sites.

Collaborators

Collaborators are involved in these and other ongoing projects and include the following:

Facilities

Our lab facilities consist of two modern laboratories outfitted with equipment for studies in physiology and endocrinology, and for gene cloning and analysis of gene expression. In addition to the usual lab equipment, we have a ABI 7300 quantitative real-time PCR machine used for measurement of mRNA, regular and gradient thermal cyclers, gel rigs and gel documentation equipment, metabolic shakers, several centrifuges, enzyme and ultracold freezers, tissue culture incubators and a sterile, laminar flow hood, equipment for histology, immmunohistochemistry and in situ hybridization, and Macintosh and PC computers. Shared facilities and equipment include autoclaves, dishwashers and ice machines. Fish holding facilities are available in the main hatchery, and a recirculating system under development will be housed adjacent to Fisheries Teaching and Research. The SAF facility at Big Beef Creek is also available to researchers.