Biomedical subjects

E M Donaldson

Publications and source records attributed to E M Donaldson.

At least 19 recordsLinked to original sources

PubMed1999

Effects of the aromatase inhibitor Fadrozole on plasma sex steroid secretion and ovulation rate in female coho salmon, Oncorhynchus kisutch, close to final maturation.

Plasma levels of 17beta-estradiol, 17alpha, 20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-P), and testosterone were measured in adult female coho salmon in late vitellogenesis, approximately 1.5 months before spawning and just before and following intraperitoneal injection with the aromatase inhibitor (AI) Fadrozole. Injection at dosages of 0.1, 1.0, and 10.0 mg AI/kg body wt caused a significant drop in plasma 17beta-estradiol levels relative to preinjection values within 3 or 6 h. Injection of 10 mg AI/kg body wt caused a significant increase in plasma 17alpha-20beta-P levels within 3 h. Ten days after injection 67% of the fish treated with 10 mg AI/kg body wt had ovulated in contrast with 0% in the group injected with 0.1 mg AI/kg body wt. The fertilization rate of the eggs varied between 96% in the control group and 85% in the groups injected with AI. We conclude that the shift from 17beta-estradiol to 17alpha,20beta-P biosynthesis, which is characteristic of maturing Oncorhynchus sp., was advanced significantly by treatment with AI and that Fadrozole can be used as a tool to investigate periovulatory endocrine changes in salmon.

Animals↗

PubMed1997

The effect of the aromatase inhibitor fadrozole and two polynuclear aromatic hydrocarbons on sex steroid secretion by ovarian follicles of coho salmon.

A variety of endogenous and exogenous factors can influence sex steroid production by salmon ovarian follicles and ultimately impact reproductive development. We examined the effect of an aromatase inhibitor, fadrozole, and common environmental contaminants (PAHs) on sex steroid secretion by ovarian follicles. Ovarian follicles of coho salmon were incubated in vitro with various concentrations of testosterone (0.10-0.40 microM) and fadrozole (10 and 100 microM), or with varying doses (between 0.05 and 5.0 microM) of the PAHs beta-naphthoflavone (BNF) and 20-methylcholanthrene (20-MC). 17 beta-Estradiol secretion was significantly reduced when follicles were incubated in the presence of fadrozole, BNF, or 20-MC. In contrast, 17 beta-estradiol production by ovarian follicles increased in a dose-dependent manner when incubated with increasing doses of the aromatizable androgen testosterone. Although increasing doses of PAHs significantly reduced follicular 17 beta-estradiol production no effect on testosterone secretion was observed. Hence, both fadrozole and PAHs can significantly reduce 17 beta-estradiol secretion by salmon ovarian follicles and may affect female sexual development.

Animals↗

PubMed1996

Plasma steroid and corticosteroid levels in female pacu Piaractus mesopotamicus, Teleostei-Characidae.

We report the plasma levels of estradiol-17 beta (E2), testosterone (T), 17 alpha-20 beta-dihydroxy-4-pregnen-3-one (17-20P), and cortisol (F) in female pacu during the reproductive cycle (N = 44) and in females induced to ovulate with an analogue of luteinizing hormone releasing hormone (LHRHa; 10 micrograms/kg) (N = 24). The plasma hormone levels were determined by validated radioimmunoassays. Females sampled during the reproductive cycle were grouped into 4 gonadal stages: resting, early maturation, advanced maturation and regression. The calculated gonadosomatic index varied from 0.5 +/- 0.1% in resting stage to 8.1 +/- 0.6% in advanced maturation stage. The E2 and T values were highest during the early maturation stage (E2 = 2172 +/- 7.1 pg/ml; T = 412 +/- 58 pg/ml) and the F values were highest during the advanced maturation stage (132 +/- 5 ng/ml). Females induced to ovulate by LHRHa injection were sampled at 0.6, and 12 h after injection of LHRHa. Two additional groups were sampled at ovulation and 24 h after ovulation. The E2 values were highest at 6 h (2917 +/- 65 pg/ml). The T and F values were highest at ovulation (T = 3498 +/- 77 pg/ml; F = 387 +/- 16 ng/ml) and 17-20P was detected only at ovulation (2163 +/- 80 pg/ml).

Analysis of Variance↗

PubMed1995

Increases in gill cytosolic corticosteroid receptor abundance and saltwater tolerance in juvenile coho salmon (Oncorhynchus kisutch) treated with growth hormone and placental lactogen.

Juvenile coho salmon (Oncorhynchus kisutch) were injected with one of two recombinant bovine hormones, growth hormone (bGH; 5.0 and 0.5 micrograms.g-1 body wt) or placental lactogen (bPL; 5.0, 0.5, and 0.05 micrograms.g-1 body wt) to determine the effect on growth, plasma cortisol concentration, cytosolic corticosteroid receptors (CR) in the gills, and the development of hypoosmoregulatory ability. One week following a single injection or six weekly injections of bGH or bPL, the fish were measured and sampled for CR concentration and Na+,K(+)-ATPase activity in the gills. Fish were also challenged with salt water (salinity 25%) for 24 hr to determine saltwater tolerance at the end of the 6-week treatment. Treatment with bPL and bGH significantly increased weight and length of the fish. The 0.05-micrograms bPL dose significantly elevated plasma cortisol concentration, whereas all other hormone treatments did not affect cortisol levels. bPL and bGH also significantly increased CR concentration and Na+,K(+)-ATPase activity in the gills. The perturbation in plasma sodium concentration was least in animals receiving the highest dose of bPL and the bGH-treated animals following transfer to seawater. An increase in cytosolic CR by bGH and bPL may increase responsiveness of the gills to cortisol and partially account for the increase in Na+,K(+)-ATPase activity and greater ability to regulate plasma sodium in seawater as exhibited by the experimental groups.

Animals↗

PubMed1994

Bovine placental lactogen is a potent stimulator of growth and displays strong binding to hepatic receptor sites of coho salmon.

Juvenile coho salmon were treated with bovine placental lactogen (bPL) and bovine growth hormone (bGH) to examine the growth promoting activities of these proteins in a lower vertebrate. Fish were intraperitoneally injected either with 0.5 or 5.0 micrograms/g bPL or with 5.0 micrograms/g bGH once a week for 5 weeks. After only a single injection and 1 week of growth, the high dose of bPL stimulated a significant increase in weight and length relative to untreated fish or fish treated with a control protein, bovine serum albumin. At the end of the experiment, all hormone-treated groups were significantly larger than controls. Fish treated with 5 micrograms/g bPL gained more than three times as much weight as controls. The 5.0 micrograms/g bGH group grew at the same rate as fish treated with one-tenth this dose of bPL, indicating that bPL is a potent stimulator of growth in this species. Radioreceptor assays performed on coho salmon liver membrane preparations indicate that bPL binds with approximately 430-fold higher affinity than bGH, and some 8000-fold higher affinity than bovine prolactin. The action of bPL relative to the structure and function of salmonid pituitary hormones is discussed.

Animals↗

PubMed1994

A radioimmunoassay for oncorhynchid growth hormone targeted to the physiological range.

This study describes the development of an oncorhynchid growth hormone (GH) radioimmunoassay using recombinant chum salmon GH (rsGH) and a rabbit antiserum (TJK-1) raised against this recombinant material. The assay was designed to measure the wide range of circulating immunoreactive GH (IRGH) levels in Pacific salmonids, resulting in a standard curve capable of accurately determining plasma levels of IRGH from 0.5 to 250 ng/mL without dilution. The assay ED50 and ED90 values averaged 13.1 and 0.5 ng/mL, respectively. This radioimmunoassay specifically recognizes oncorhynchid IRGH, showing no cross-reactivity with recombinant porcine and bovine GH, or natural chum salmon prolactin at concentrations up to 10 micrograms/mL. Curves approximately parallel to the standard curve were obtained with purified natural coho salmon GH and plasma from chinook salmon. Recovery of rsGH from plasma was complete over the full range of the standard curve. Intra- and inter-assay coefficients of variation were 6.0 and 12.9%, respectively. Plasma IRGH levels in fed coho salmon were 30.6 +/- 5.3 ng/mL, while those in fish starved for 2 weeks were 132.9 +/- 53.9 ng/mL. Starvation for an additional 4 weeks had no significant effect. Plasma IRGH levels in control rainbow trout injected with saline were significantly higher 45 min post-injection. In contrast, fish injected with recombinant porcine GH exhibited no elevation in IRGH. It is speculated that exogenous GH inhibits the production of endogenous GH.

Animals↗

PubMed1993

Effects of natural, synthetic, aromatizable, and nonaromatizable androgens in inducing male sex differentiation in genotypic female chinook salmon (Oncorhynchus tshawytscha).

The relative potency of several androgens to induce the male phenotype in sexually undifferentiated genotypic female chinook salmon were compared in two separate experiments. The aromatizable and nonaromatizable androgens testosterone (T) and 11-ketotestosterone (11-KT), and the synthetic aromatizable and nonaromatizable androgens 17 alpha-methyltestosterone (MT) and 17 alpha-methyldihydrotestosterone (MDHT) were administered to newly hatched alevins in a single 2-hr immersion treatment at doses ranging from 3.2 micrograms/liter to 10 mg/liter. The influence of these treatments on sex differentiation was evaluated by the histological examination of the resulting gonads 6 and 11 months later. In the control group, which was not exposed to exogenous steroids, no males or intersex fish were observed. In contrast, essentially 100% masculinization occurred in groups exposed to MDHT at dosages of 400 micrograms/liter and higher. Treatment with the aromatizable androgen MT resulted in a dose-dependent masculinization, with the production of 100% males at 400 micrograms/liter. However, higher doses resulted in fewer males. 11-KT and T were less potent than the synthetic androgens. The number of males produced after treatment with 11-KT followed a dose-dependent pattern while T showed virtually no masculinizing effect in inducing male phenotype in these studies. The resultant AD50 dosage levels (dosage at which 50% of the genotypic females were sex-reversed into phenotypic males) after a single 2-hr immersion treatment were: 30, 60, and 500 micrograms/liter for MDHT, MT, and 11-KT, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗

PubMed1990

Toward the origin of the secondary palate. A possible homologue in the embryo of fish, Onchorhynchus kisutch, with description of changes in the basement membrane area.

The oral cavity of embryos and larvae of the teleost Onchorhynchus kisutch was examined. Tissues were obtained at different ages prior to and after hatching and processed for transmission and scanning electron microscopy. A bilaterally symmetrical bulge developed from the superolateral aspect of the oral cavity and projected toward its floor, along the sides of the tongue. The bulge extended from behind the primary palate to a position midway below the eye, anterior to the gill arches, and it is suggested to be the homologue of the secondary palate of higher vertebrates. Ultrastructurally, the epithelium differentiated as the stratified squamous type and it contained mucous cells. However, the features of programmed cell death seen during palatogenesis in mammals were absent in fish. The fish palate mesenchyme, unlike that of higher vertebrates, was chondrified. Also in contrast to higher vertebrates, alterations were seen in the fish palatal basement membrane. A transient appearance of adepidermal granules in the lamina lucida region was followed by organization of collagen fibrils, first into an orthogonal pattern and then into a herring-bone arrangement, in the lamina reticularis region. There was no further advancement in the morphogenesis of fish palate. It is suggested that the differences in the morphogenesis and structure of the secondary palates of various vertebrates may reflect environmentally enforced adaptation, resulting in different programming of cells.

Animals↗

PubMed1989

An homologous radioimmunoassay for coho salmon (Oncorhynchus kisutch) vitellogenin, with general applicability to other Pacific salmonids.

This paper describes an homologous radioimmunoassay for coho salmon vitellogenin that demonstrates parallel cross-reactivity for plasma vitellogenin of all Pacific salmonids tested (chinook, chum, coho, pink, and sockeye salmon, and cutthroat and rainbow trout), but not for Atlantic salmon or two nonsalmonids: common carp and sablefish. Plasma vitellogenin levels were high in ovulatory female Pacific salmonids (micrograms/ml to mg/ml range), but were mostly nondetectable in spermiating males of the same species.

Animals↗

PubMed1989

Estrogen-induced vitellogenin production by triploid coho salmon (Oncorhynchus kisutch), and its effect on plasma and pituitary gonadotropin.

Vitellogenin production was induced in immature diploid and triploid coho salmon by the weekly injection of 17 beta-estradiol at 1 mg/kg body wt. There was no significant difference between diploids and triploids for any of the results obtained, i.e., change in plasma vitellogenin and gonadotropin levels, hepatosomatic index, or pituitary gonadotropin content. Plasma vitellogenin levels were significantly higher in 17 beta-estradiol-treated fish than in sham-injected fish within a week of the first injection, and continued to rise with each subsequent injection. Plasma gonadotropin levels, on the other hand, were slightly (but significantly) depressed. The 17 beta-estradiol-treated fish had higher hepatosomatic indices and pituitary gonadotropin contents than sham-injected fish by 3 weeks after the first treatment. These data suggest that the occasional postmeiotic oocytes observed in triploids do not grow to full maturity due, in part, to an absent or diminished estrogen stimulus from the ovary on hepatic vitellogenin production.

Animals↗

PubMed1986

The development and validation of a radioimmunoassay to measure plasma ACTH levels in salmonid fishes.

A radioimmunoassay (RIA) capable of determining blood ACTH levels in salmonid fishes was developed and validated. The RIA used an antibody raised against mammalian ACTH, iodinated human ACTH as tracer, and human 1-39 ACTH as standard. Incubation of the standard or unknown with antibody for 3 days before addition of as little high-specific activity tracer as practicable (1500 cpm; equivalent to 5 pg ACTH) produced a very sensitive RIA; the operating range was 5 to 200 pg ACTH/ml. Extracts of both pars distalis and neurointermediate lobe of the pituitary glands from a range of salmonid species diluted parallel to the ACTH standard in the RIA. There was always considerably more ACTH-immunoreactivity (ACTH-IR) in the pars distalis extracts than in the neurointermediate lobe. Generally plasmas also diluted parallel to the ACTH standard, with the exception only of the plasma from sexually mature female salmonids, which diluted very non-parallel to the standard, leading to unrealistically low estimates of the ACTH-IR level. The use of heparin as an anticoagulant during collection of samples caused problems when these plasmas were immunoassayed; instead EDTA was found to be a suitable anticoagulant. When the ACTH-IR was extracted from a pool of plasma obtained from acutely stressed salmon and chromatographed on a column of BioGel P6, followed by subsequent ACTH RIA of the fractions, only a single sharp peak of ACTH-IR was detected, which eluted in the position of authentic 1-39 ACTH. The plasma ACTH-IR level in unstressed fish was low, and near the detection limit of the RIA. An acute stress, produced by crowding and confinement for 30 min, increased ACTH-IR approximately 10-fold, and plasma cortisol levels 50-fold, but the plasma alpha-MSH level was not affected. Dexamethasone-treated fish did not respond to this stressor with any increase in either ACTH or cortisol levels.

Adrenocorticotropic Hormone↗

PubMed1984

Effects of LH-RH and Des-Gly10[D-Ala6]LH-RH-ethylamide on plasma sex steroid profiles in adult female coho salmon (Oncorhynchus kisutch).

17 beta-Estradiol, testosterone, and 17 alpha, 20 beta dihydroxy-4-pregnen-3-one (17 alpha 20 beta P) levels were measured in plasma samples obtained from coho salmon (Oncorhynchus kisutch) during the preovulatory period and following the injection of mammalian gonadotropin releasing hormones. Spontaneous reproductive activity was characterized by a rapid decline in plasma 17 beta-estradiol 10 days prior to ovulation and a large increase in plasma 17 alpha 20 beta P 6 days before ovulation. Testosterone levels remained high (greater than 125 ng/ml) throughout the preovulatory period, with a small peak evident 6 days prior to ovulation. Oocyte development was not accelerated in fish injected with mammalian LH-RH, whereas des-Gly10[D-Ala6]LH-RH-ethylamide (LH-RHA DAla6) promoted germinal vesicle breakdown (GVBD) in 10 out of 14 fish within 96 hr. Only LH-RHA DAla6-injected fish which completed GVBD displayed the characteristic steroid changes observed during spontaneous reproductive activity. In LH-RH-injected fish, there was a transient increase in plasma 17 alpha 20 beta P levels which persisted for less than 24 hr. LH-RHA DAla6-injected fish which failed to complete GVBD maintained high 17 alpha 20 beta P levels, but the peak concentrations were lower than those in fish which completed GVBD. These fish also maintained high plasma 17 beta-estradiol levels when compared to fish which completed GVBD. The appearance of high plasma 17 alpha 20 beta P levels during spontaneous and LH-RHA DAla6-induced reproductive activity was coincident with the time of GVBD. This finding was consistent with the view that 17 alpha 20 beta P functions as the maturation-inducing steroid in salmonids. The induction of GVBD using gonadotropin-releasing hormones was related to the elevation of plasma gonadotropin levels for greater than 24 hr [G. Van Der Kraak, H. R. Lin, E. M. Donaldson, H. M. Dye, and G. A. Hunter (1983) Gen. Comp. Endocrinol. 49, 470-476] and a decrease in 17 beta-estradiol production.

Animals↗

PubMed1983

Effects of LH-RH and des-Gly10[D-Ala6]LH-RH-ethylamide on plasma gonadotropin levels and oocyte maturation in adult female coho salmon (Oncorhynchus kisutch).

Plasma gonadotropin (GtH) levels and state of oocyte development were determined in adult female coho salmon following single intraperitoneal injections of LH-RH or its superactive analog des-Gly10[D-Ala6]LH-RH-ethylamide (LH-RHA DAla6). The peptides injected at dosages of 1.0 or 0.2 mg LH-RH and 0.2 or 0.02 mg LH-RHA DAla6/kg bw elevated plasma GtH by 1.5 hr postinjection. The response to the analog was of longer duration. Plasma GtH levels returned to basal levels 24 hr following LH-RH injection while elevated plasma GtH levels were maintained for at least 96 hr in response to the analog. Only those fish injected with LH-RHA DAla6 showed an accelerated rate of germinal vesicle breakdown (GVBD). Based on their relative effects on GVBD, LH-RHA DAla6 has at least 50 times the biological potency of LH-RH in adult female coho salmon.

Animals↗

PubMed1981