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W W Dickhoff

Publications and source records attributed to W W Dickhoff.

At least 37 records · Page 2Linked to original sources
PubMed1995

Isolation and characterization of insulin-like growth factor-I from rainbow trout, Oncorhynchus mykiss.

Insulin-like growth factor-I (IGF-I) has been purified from plasma of adult rainbow trout, Oncorhynchus mykiss. Plasma samples were collected 48 hr following injection of recombinant tuna growth hormone at a dose of 0.5 microgram/g body weight. Acid-ethanol extract of plasma was fractionated by gel filtration on a Sephadex G-50 superfine column. Two-step ion-exchange chromatography on DEAE-52 and then Mono-S columns followed. Rainbow trout IGF-I was further purified by immunoaffinity chromatography with anti-recombinant coho salmon IGF-I (rsIGF-I) serum and HPLC on a reverse-phase C18 column. During purification, trout IGF-I was monitored by SDS-PAGE, immunoblotting with anti-IGF-I-serum, homologous radioimmunoassay (RIA) for salmon IGF-I, and sulfation bioassay. The trout IGF-I appeared on SDS-PAGE as a single band with a molecular weight of 7 kDa, the same size as rsIGF-I. The partial N-terminal amino acid sequence (residues 1-20) was identical to the predicted mature trout IGF-I cDNA sequence. Trout IGF-I cross-reacted with anti-rsIGF-I serum in immunoblotting and its dilution curve was parallel to the rsIGF-I standard curve in salmon RIA. In concentrations of 50 and 500 ng/ml, trout IGF-I significantly stimulated sulfation uptake by the cultured branchial cartilage of rainbow trout. This stimulatory effect of trout IGF-I was dose-dependent and similar in its biological potency to rsIGF-I.

Amino Acid Sequence↗
PubMed1995

Expression of insulin-like growth factor I in normally and abnormally developing coho salmon (Oncorhynchus kisutch).

Changes in levels of insulin-like growth factor-I (IGF-I) messenger RNA (mRNA) in tissues of normally and abnormally growing (stunted) juvenile coho salmon in seawater were studied. Profiles of hepatic IGF-I mRNA levels were compared with changes in growth and plasma concentrations of GH and insulin. In normally growing fish, IGF-I mRNA levels, as measured by solution hybridization-RNase protection assay, showed that hepatic IGF-I mRNA levels of yearling salmon were highest in May and June. Increased hepatic IGF-I mRNA levels followed increases in both plasma GH and insulin. Levels of hepatic IGF-I mRNA decreased in July, after a sharp decline in plasma GH in June, and remained low until the following spring. The growth rate for normal fish also decreased during fall and winter. After increases in plasma GH and insulin, which peaked in late February, hepatic IGF-I mRNA levels increased rapidly and reached a second peak in April. Increases in plasma GH and hepatic IGF-I mRNA observed in the second year were smaller and occurred earlier than in the first spring in seawater. Growth retardation (stunting) resulted from the premature transfer of cultured fish to seawater. Compared with normally growing fish, these stunted salmon had significantly higher levels of plasma GH but lower levels of plasma insulin. Hepatic IGF-I mRNA levels in stunted salmon were significantly lower, despite elevated plasma GH levels. These results indicate that hepatic levels of IGF-I mRNA in juvenile coho salmon increase in springtime, after an increase in plasma GH and insulin. These seasonal increases in GH and IGF-I precede the rapid growth period coinciding with the springtime increases in temperature and photoperiod and may therefore be associated with these environmental cues. The elevated plasma GH and reduced hepatic IGF-I mRNA levels observed in growth-retarded salmon suggested that stunted salmon may be GH resistant. Hepatic GH resistance and diminished IGF-I production may be the central endocrine defects leading to growth retardation in stunted salmon.

Animals↗
PubMed1994

Development of a homologous radioimmunoassay for coho salmon insulin-like growth factor-I.

A specific homologous radioimmunoassay (RIA) for measurement of insulin-like growth factor-I (IGF-I) in plasma of salmonid and a few non-salmonid fish species was developed using recombinant coho salmon IGF-I (rsIGF-I) as tracer and standard, and antiserum against this peptide raised in rabbits. The minimum detection level of IGF-I was 1.5 ng/ml and linearity was obtained in a range from 1.5 to 23 ng/ml. No cross-reaction was detected in the salmon IGF-I RIA with mammalian growth factors, salmon pituitary hormones, salmon or mammalian insulin, or any peptide in rat plasma. Although salmon IGF-I has high sequence similarity to mammalian IGF-I, it did not cross-react with anti-human IGF-I serum in human RIA and serial dilutions of plasma from salmon were not parallel to the human IGF-I standards in this assay system. In contrast, dilution curves for plasma of salmonids, such as coho (Oncorhynchus kisutch), Atlantic (Salmo salar), and sockeye (O. nerka) salmon, rainbow trout (O. mykiss), some other teleost fish, such as tilapia (Oreochromis mossabmica), carp (Cyprus carpio), eel (Anguilla rostrata), Atlantic halibut (Hippoglossus hippoglossus), and agnathan, the sea lamprey (Petromyzon marinus), assessed in salmon IGF-I RIA were parallel to the rsIGF-I standards. Acid-ethanol extraction of plasma samples altered the molecular weight, but not the quantity, of immunoreactive IGF-I, implying that IGF-I binding proteins in salmon plasma do not affect the performance of the salmon IGF-I RIA. Gel filtration of nonacidified plasma on a Sephadex G-75 superfine column produced two immunoreactive IGF-I peaks of molecular weights of approximately > 70 k and 7 kDa, whereas acidification of plasma increased the relative amount of the 7-kDa peak (IGF-I) and the > 70-kDa peak disappeared. The recoveries of rsIGF-I added to extracted or nonextracted plasma were 97.4 and 94.9%, respectively. Inter- and intraassay coefficients of variation were 3.6 and 3.3%, respectively. Plasma IGF-I levels in coho salmon smolts were 117.4 +/- 19.1 ng/ml as compared to IGF-I levels in parr (45.3 +/- 2.5 ng/ml) or in adult fish (45.2 +/- 5.4 ng/ml) measured in the same assay. Injection of salmon growth hormone, but not prolactin or somatolactin, caused a significant and dose-dependent elevation of plasma IGF-I levels, while either fasting or injection of streptozotocin led to a significant decline in systemic IGF-I.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Differential expression and hormonal regulation of alternatively spliced IGF-I mRNA transcripts in salmon.

Salmon have been shown to express alternatively spliced IGF-I mRNA transcripts coding for four different IGF-I prohormones. These transcripts, now designated Ea-1, Ea-2, Ea-3 and Ea-4, differ in size due to the inclusion of additional sequences in the E domain-coding region of the molecule. In this study, the tissue distribution and hormonal regulation of expression of alternatively spliced IGF-I mRNA transcripts were investigated in coho salmon. IGF-I mRNAs were detected by solution hybridization/RNase protection assay in all tissues examined. GH treatment significantly increased hepatic IGF-I mRNA content. Hepatic IGF-I mRNA levels were not influenced by prolactin or somatolactin. Heart, fat, brain, kidney, spleen and ovary IGF-I mRNA levels were not affected by GH, prolactin or somatolactin. Ea-1, Ea-3 and Ea-4 mRNA transcripts were detectable in the liver, and Ea-1 and Ea-3 levels increased dramatically in response to GH treatment, whereas the amount of Ea-4 mRNA was unchanged. Most non-hepatic tissues expressed only the Ea-4 transcript, and expression was not influenced by GH, prolactin or somatolactin. Ea-1 and Ea-3 transcripts were visible in gill samples from fish treated with GH. The ovaries of juvenile fish expressed Ea-1, Ea-2 and Ea-4. The amounts of these transcripts were not changed by gonadotrophin treatment. During smoltification of juvenile coho salmon, liver and gill IGF-I mRNA levels increased with increasing plasma GH and thyroxine concentrations. Muscle, brain and ovary IGF-I mRNA levels were unchanged during this period. These data suggest that the liver is a major site of IGF-I production in response to GH. Heart, fat, brain, kidney, spleen and ovary did not show increased IGF-I mRNA levels in response to GH treatment. GH and prolactin had inconsistent effects on muscle IGF-I mRNA levels. Somatolactin and a gonadotrophin preparation did not stimulate IGF-I expression in tissues of juvenile fish. Differences in tissue GH responsiveness can be partially explained by the expression of alternatively spliced IGF-I mRNAs. Of the four hepatic IGF-I mRNA transcripts, Ea-1 and Ea-3 are GH-responsive, while Ea-2 and Ea-4 are not. Most non-hepatic tissues express only the Ea-4 transcript, and IGF-I mRNA levels do not increase after GH treatment. The increased IGF-I mRNA levels observed in gill tissue during smoltification suggest that other factors, in addition to GH, may regulate IGF-I expression.(ABSTRACT TRUNCATED AT 400 WORDS)

Alternative Splicing↗
PubMed1993

Recombinant coho salmon insulin-like growth factor I. Expression in Escherichia coli, purification and characterization.

Recombinant coho salmon insulin-like growth factor I (rsIGF-I) was produced in Escherichia coli, purified and characterized. The rsIGF-I expression vector was constructed by polymerase chain reaction and cloning into a plasmid containing a phage T7 RNA polymerase promoter. The rsIGF-I was recovered from bacterial inclusion bodies, solubilized under reducing conditions, immediately refolded, then fractionated by a two-step ion-exchange chromatography on DEAE-52 and Mono-S columns. It was further purified by HPLC on a reverse-phase Asahi-Pak C4P-50 C4 column. Purification of rsIGF-I was monitored by SDS/PAGE and immunoblot with anti-[human somatomedin C (SM C)/IGF-I] serum. The rsIGF-I appeared as a single band with molecular mass of 7 kDa, the same size as recombinant human IGF-I (rhIGF-I) and cross-reacted with anti-(human SM C/IGF-I) serum. The amino acid sequence of rsIGF-I contained an NH2-terminal methionine residue followed by the sequence predicted for mature sIGF-I. At concentrations in the range 3.9-250 ng/ml, rsIGF-I significantly stimulated sulfate uptake by the cultured branchial cartilage of coho salmon. The stimulatory effect of rsIGF-I was concentration dependent and slightly more potent than that of rhIGF-I at the highest concentration tested.

Amino Acid Sequence↗
PubMed1993

Regulation of testicular steroid production in vitro by gonadotropins (GTH I and GTH II) and cyclic AMP in coho salmon (Oncorhynchus kisutch).

The ability of coho salmon gonadotropins GTH I and GTH II to stimulate testicular production of 11-ketotestosterone (11-KT) and 17 alpha,20 beta-dihydroxy-4- pregnen-3-one (17,20 beta-P) in vitro, as well as the involvement of cyclic AMP (cAMP) as a mediator of the actions of GTH I and GTH II, were investigated in maturing male coho salmon. Testicular tissue was incubated in the presence or absence of the test substances at 15 degrees. Both GTH I and GTH II stimulated the in vitro production of 11-KT and 17,20 beta-P in a concentration- and time-dependent manner. In testicular tissue at stage IV of spermatogenesis, GTH I and GTH II stimulated the in vitro production of steroids with similar potency. The steroidogenic activity of GTH I and GTH II appeared to be mediated, at least in part, by cAMP as indicated by the ability of dibutyryl cAMP and forskolin to mimic the steroidogenic actions of GTHs, and the similar ability of GTH I and GTH II to increase intracellular cAMP levels in the testicular tissue. The calcium ionophore A23187 stimulated basal but not GTH-stimulated production of steroids in vitro. In addition, differential effects of a protein kinase C inhibitor, H-7, on 11-KT and 17,20 beta-P production were found. Basal and GTH-stimulated production of 11-KT were inhibited by H-7; whereas basal and GTH-stimulated production of 17,20 beta-P were stimulated by H-7. These results suggest that protein kinase C may also be involved in the steroidogenic actions of GTH I and GTH II.

Animals↗
PubMed1992

Somatolactin stimulates in vitro gonadal steroidogenesis in coho salmon, Oncorhynchus kisutch.

Somatolactin (SL), a newly discovered pituitary hormone of the teleost pars intermedia, is structurally similar to prolactin and growth hormone. The function(s) of SL are not yet established, although evidence suggests that it may play a role in reproduction. Possible steroidogenic activity of coho salmon SL was tested and compared with gonadotropin I (GTH I) in incubations of ovarian follicles or testicular fragments. SL stimulated production of 11-ketotestosterone and testosterone by testicular fragments, and production of estradiol by ovarian follicles in a concentration-dependent manner. However, the steroidogenic activity of SL was considerably less than that of GTH I. These results suggest that SL may play a role in regulation of gonadal function in salmon.

Animals↗
PubMed1992

A two-receptor model for salmon gonadotropins (GTH I and GTH II).

The possible existence of distinct receptors for salmon gonadotropins (GTH I and GTH II) and the distribution of the receptor(s) were studied through examination of the binding of coho salmon (Oncorhynchus kistuch) GTH I and GTH II to membranes from thecal layers and granulosa cells of salmon ovaries. Purified coho salmon gonadotropins were iodinated by the lactoperoxidase method. Crude membrane preparations were obtained from thecal layers, granulosa cells, and whole ovaries of coho salmon in the postvitellogenic/preovulatory phase. Binding of 125I-GTH I to membranes from thecal layers, granulosa cells, and whole ovaries, and binding of 125I-GTH II to thecal layer cell membranes could be inhibited by both GTHs, but GTH I was more potent than GTH II. In contrast, GTH II was more potent than GTH I in inhibiting 125I-GTH II binding to membranes from granulosa cells and whole ovaries, but the inhibition curves were not parallel. Scatchard plot analysis suggested that there was a single type of receptor in the thecal layers for both GTHs, whereas in the granulosa cells there was more than one type of receptor for both GTHs. Based on these results, a two-receptor model for the postvitellogenic/preovulatory salmon ovary is proposed with the following features: 1) there are two types of gonadotropin receptors in the salmon ovary, type I and type II; 2) the type I receptor binds both GTHs, but with higher affinity for GTH I, whereas the type II receptor is highly specific for GTH II and may have only limited interaction with GTH I; and 3) the type I receptor is present in both thecal cells and granulosa cells, whereas the type II receptor is present in granulosa cells.

Animals↗
PubMed1992

Nucleotide sequence and tissue distribution of three insulin-like growth factor I prohormones in salmon.

Tissue distribution and potential alternative splicing of insulin-like growth factor I (IGF-I) messenger RNA were studied using reverse transcriptase-polymerase chain reaction (RT-PCR) on RNA from several tissues at various stages of the life cycle of coho salmon (Oncorhynchus kisutch). DNA sequence analysis of RT-PCR products revealed three IGF-I mRNA transcripts, designated Ea-1, Ea-2, and Ea-3, which code for three distinct prohormones, IGF-IA-1, IGF-IA-2, and IGF-IA-3, respectively. The E-domain of proIGF-IA-1 is 35 amino acids long and shares 77% sequence identity with the E-domain of human proIGF-IA, which is also 35 amino acids long. The proIGF-IA-2 and proIGF-IA-3 E-domains are homologous to the proIGF-IA-1 E-domain but contain 27 and 39 amino acid inserts, respectively, between Lys86 and Glu87. In the human IGF-I gene Lys86 is coded by exon 4 and Glu87 is coded by exon 6. This suggests that Ea-2 and Ea-3 transcripts may be the result of alternative splicing during pre-mRNA processing. All three transcripts were readily detectable using a solution hybridization/RNase protection assay. Furthermore, RT-PCR and DNA sequencing analysis indicate the presence of three IGF-I prohormones in another member of the Salmonidae family, the Atlantic salmon (Salmo salar). An analysis of IGF-I and -II E-domains from several vertebrates suggests that certain chemical and physical properties of the molecule are well conserved despite wide variations in primary structure. Ea-1, Ea-2, and Ea-3 transcripts were found in whole embryos, and liver, muscle, and brain of juvenile and adult salmon. At least one IGF-I transcript was found in heart, kidney, testes, ovary, adipose tissue, and spleen of juvenile salmon. These results indicate that IGF-I is expressed during embryonic development of fish, and that most tissues are capable of IGF-I mRNA production. These data also indicate that pre-mRNA transcripts can be alternatively spliced to yield at least three prohormones.

Alternative Splicing↗
PubMed1992

Somatolactin, a novel pituitary protein: purification and plasma levels during reproductive maturation of coho salmon.

Somatolactin (SL), a newly discovered fish pituitary protein belonging to the GH/prolactin family, was isolated from coho salmon (Oncorhynchus kisutch). Antibodies were raised to purified coho SL, and a homologous radioimmunoassay was developed and validated. The assay was specific for SL as indicated by the absence of cross-reactivity with coho salmon GH, gonadotrophins I and II and less than 0.2% cross-reaction to prolactin. Serial dilutions of plasma and pituitary extracts from Oncorhynchus species including coho salmon, chinook salmon and rainbow trout were parallel to the coho salmon SL standard curve. Displacement curves for dilutions of Atlantic salmon (Salmo salar) plasma, but not pituitary extract were parallel to the standards. Plasma levels of SL were measured in coho salmon throughout the final year of reproductive maturation. During the period of gonadal growth, plasma SL levels increased and were highly correlated to oestradiol levels in females and 11-ketotestosterone levels in males. Peak levels of SL were observed at the time of final maturation and spawning in both sexes. It is hypothesized that SL may regulate some physiological aspect of reproduction.

Amino Acid Sequence↗
PubMed1991

Developmental differences in the responsiveness of gill Na+,K(+)-ATPase to cortisol in salmonids.

The ability of cortisol to increase gill Na+,K(+)-ATPase activity was examined in several salmonid species during development. Coho salmon (Oncorhynchus kisutch) parr were unresponsive to cortisol in vitro (10 micrograms/ml for 2 days) in November. Responsiveness was significant from January to March, peaking in January just prior to seasonal increases in gill Na+,K(+)-ATPase activity. Gill tissue became unresponsive to in vitro cortisol in April when in vivo gill Na+,K(+)-ATPase activity peaked. The ability of cortisol to stimulate gill, Na+,K(+)-ATPase activity in postemergent fry (2-3 months after hatching) was examined in chum (O. keta), chinook (O. tschawytscha), coho, and Atlantic salmon (Salmo salar). Initial levels of gill Na+,K(+)-ATPase activity were elevated in chum salmon, which normally migrate as fry. Cortisol (10 micrograms/ml for 4 days in vitro) increased gill Na+,K(+)-ATPase activity in chum salmon fry (48% above initial levels), had a limited but significant effect in chinook salmon fry, and had no effect in coho and Atlantic salmon fry. In an in vivo experiment, Atlantic salmon previously exposed to simulated natural photoperiod (SNP) and continuous light (L24) received four cortisol injections of 2 micrograms.g-1 every third day. SNP fish responded with increased gill Na+,K(+)-ATPase activity (+66%), whereas L24 fish were not affected. Atlantic salmon presmolts with initially low levels of gill Na+,K(+)-ATPase activity responded to cortisol in vitro, whereas smolts with initially high levels of gill Na+,K(+)-ATPase activity were unresponsive.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Isolation and characterization of two coho salmon gonadotropins, GTH I and GTH II.

Two gonadotropins, GTH I and GTH II, were isolated from pituitaries of spawning coho salmon (Oncorhynchus kisutch) using sequential extractions with ammonium acetate (pH 9.0) and 40% ethanol, precipitation with 80% ethanol, gel filtration chromatography (Sephadex G-100), anion-exchange chromatography (Mono-Q Sepharose), and gel filtration chromatography (Sephadex G-75). Coho salmon GTH I and GTH II stimulated steroidogenesis in vitro in a similar dose-dependent manner when incubated with either ovaries or testes of prepubertal coho salmon. An in vivo bioassay using coho salmon parr demonstrated that coho salmon GTH I and GTH II did not contain thyrotropic activity. Molecular weights were estimated by gel filtration chromatography to be 43,000 and 39,000 for GTH I and GTH II, respectively. Analysis of coho salmon GTH I and GTH II on reversed-phase high-performance liquid chromatography (rpHPLC) revealed that they consist of alpha and beta subunits with N-terminal amino acid residues of Tyr, Gly (alpha, beta of GTH I) and Tyr,Ser (alpha, beta of GTH II). Coho salmon GTH I-beta and GTH II-beta differed from each other in amino acid composition, N-terminal amino acids (Gly vs. Ser), and molecular weights in SDS-PAGE (19,000 vs. 20,000) and had a high degree of chemical similarity to chum salmon GTH I-beta and GTH II-beta, respectively. Specific rabbit antisera to the beta subunits of coho salmon GTH I and GTH II were generated. The observation of two GTHs with distinctly different chemical characteristics in coho salmon is similar to what has previously been found in chum salmon.

Amino Acids↗
PubMed1990

Salmonid pituitary gonadotrophs. II. Ontogeny of GTH I and GTH II cells in the rainbow trout (Salmo gairdneri irideus).

Immunocytochemistry of rainbow trout pituitary gonadotrophs (GTH I- and GTH II-producing cells) during gametogenesis was investigated. GTH I and GTH II were found in distinctly different cells in all stages of reproductive development that were examined. Only GTH I cells were present in trout prior to puberty. GTH II appeared in addition to GTH I coincident with the onset of vitellogenesis and spermatogenesis. Both GTH I and GTH II cells were found in trout at the time of final reproductive maturation, although the number of GTH II cells was greater than that of GTH I cells. These data indicate that GTH I and GTH II are localized in separate cells in the trout pituitary throughout gametogenesis, and that synthesis of GTH I and GTH II varies during reproductive development.

Animals↗
PubMed1988

Thyrotropic activity of salmon pituitary glycoprotein hormones in the Hawaiian parrotfish thyroid in vitro.

The thyrotropic activities of salmon pituitary extract, thyroid-stimulating hormone (TSH), gonadotropins (GTH), and glycoprotein fractions obtained during purification of salmon TSH and GTH were measured using the parrotfish thyroid culture system. Purified salmon TSH was approximately 1,000 times more potent than bovine TSH in stimulating thyroxine release into the culture medium. Most of the forms of salmon GTH had no thyrotropic activity. One of the forms of salmon GTH (GTH-F) and three chromatofocusing fractions (CF-B, -C, and -E) that were devoid of activity in the coho salmon in vivo had some thyrotropic activity in the parrotfish thyroid culture. Whether the activity of these fractions was due to contamination with TSH, less potent forms of TSH, or inherent thyrotropic activity of a form of GTH is discussed. These results indicate that the parrotfish thyroid culture system can be used to detect thyrotropic activity of fractions obtained during the purification of teleost TSH.

Animals↗
PubMed1987

Variation in thyroid response to thyroid-stimulating hormone in juvenile coho salmon (Oncorhynchus kisutch).

Changes in the circulating levels of thyroid hormones measured by radioimmunoassay in yearling coho salmon in response to injection of bovine thyroid-stimulating hormone (TSH) were evaluated from January through August. Doses of TSH ranging from 0.2 to 6.4 micrograms/g body wt were ineffective in stimulating T4 in January and at one time in April. Responses to TSH injection at this dose range were observed beginning in February and continuing through August. The minimal effective dose of TSH was either 0.2 or 0.4 microgram/g from May through August. The dose-response relationships of bovine and coho salmon TSH were compared and found to be similar. The time course of response of juvenile salmon to either bovine TSH or partially purified salmon TSH was found to be similar in January, May, and August, although the magnitude of the response differed at these different times. It is concluded that the increase in thyroid response to TSH may play a part in the onset of the increase in circulating T4 at the time of smoltification, but such changes in sensitivity do not explain the decrease in circulating T4 at the completion of smoltification.

Animals↗
PubMed1987

Thyroid hormones in blood plasma of developing salmon embryos.

Blood plasma thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3) concentrations in developing embryos of chum (Oncorhynchus keta), coho (Oncorhynchus kisutch), chinook (Oncorhynchus tschawytscha), and Atlantic salmon (Salmo salar) were measured by radioimmunoassay between hatching and completion of yolk-sac absorption. Blood sampling was initiated when approximately 50% of the yolk that was present at hatching had been absorbed. At this time blood plasma levels of T4 (7-9 ng/ml) and T3 (1-5 ng/ml) were similar in all species. In embryos of each salmon species blood plasma levels of T4 increased to maximal values (9-16 ng/ml) when both differentiation of the abdominal body wall and absorption of the yolk sac were completed. Blood plasma levels of T3 generally decreased to low or nondetectable values during this time. There was either a trend toward a decrease or a stasis of levels of T4 and at the same time in some species an increase in levels of T3 in the blood plasma following the completion of yolk-sac absorption and the onset of exogenous feeding. These results demonstrate that thyroid hormones are present in the blood of developing teleost embryos. This finding is discussed in light of the possible role of thyroid hormones in control of the embryonic and larval development of fishes.

Animals↗
PubMed1987

Pituitary thyrotropin and gonadotropin of coho salmon (Oncorhynchus kisutch): separation by chromatofocusing.

Thyrotropin (TSH) and gonadotropin (GTH) were isolated from adult female coho salmon pituitary glands. After final extraction in acidic alcohol and precipitation in 85% ethanol, proteins were fractionated using gel filtration chromatography and chromatofocusing. Homologous bioassay systems were used to monitor bioactivity during the purification procedures. TSH activity was measured in vivo in coho salmon parr. GTH (steroidogenic) activity was determined in vitro using cultures of adult coho salmon ovarian follicles. Using these procedures, TSH and GTH activities were separated. TSH activity eluted as one major peak at pH 6.3 whereas GTH activity eluted as five major peaks at pH's 5.4, 5.0, 4.7, 4.3, and after 1.0 M NaCl on chromatofocusing. Molecular weights of the TSH and GTHs were estimated by gel filtration chromatography as 35 and 40 kDa, respectively. Like other vertebrate TSHs and gonadotropins, the coho salmon TSH and GTHs appeared to consist of two subunits. Coho salmon TSH and bovine TSH (bTSH) were equipotent in the TSH bioassay. The five coho salmon GTHs exhibited similar potencies in stimulating ovarian estradiol synthesis in vitro. Further biochemical analysis and tests for other gonadotropic activities are warranted to determine if these five GTHs are isoforms of one GTH or if they can be distinguished functionally in other GTH bioassays. Sufficient quantities of coho salmon TSH were isolated in this study for future studies of the hypothalamic-pituitary-thyroid axis in fish.

Animals↗