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A Gorbman

Publications and source records attributed to A Gorbman.

At least 37 records · Page 2Linked to original sources
PubMed1986

Isolation and structures of coho salmon (Oncorhynchus kisutch) glucagon and glucagon-like peptide.

Glucagon and glucagon-like peptide (GLP) containing 31 amino acids have been isolated from the principal islet of coho salmon (Oncorhynchus kisutch) by gel filtration of acid alcohol extracts followed by HPLC, and the complete amino acid sequence of both peptides has been determined. Salmon glucagon is a simple 29 residue peptide differing at 3 positions when compared to catfish glucagon and at 8 positions when compared to porcine glucagon. Salmon GLP differs at 6 positions when compared with the N-terminal 31 amino acids of the 34 amino acid catfish GLP. Both coho salmon glucagon and GLP cross-react weakly in our mammalian glucagon radioimmunoassay and therefore this technique could not be used to determine tissue content. Glucagon and GLP isolated amounted to 156 micrograms/g and 350 micrograms/g wet tissue, respectively.

Amino Acid Sequence↗
PubMed1985

Steroid and thyroid hormone profiles following a single injection of partly purified salmon gonadotropin or GnRH analogues in male and female sea lamprey.

The effects of exogenous administration of gonadotropin-releasing hormone (GnRH) analogues or of a partly purified salmon gonadotropin extract (GTH) on the duration of steroid and thyroid hormone levels were determined in female and male sea lampreys, Petromyzon marinus, tested under differing temperature and reproductive status. Plasma estradiol levels, but not androgens, were significantly elevated in response to the GnRH analogues or GTH injection compared to controls in female and male lampreys. Higher temperature and/or advance in time of maturation appeared to be inversely related to plasma estradiol levels. These data provide further evidence of hypothalamic control over reproductive function in lampreys. Plasma thyroxine was significantly elevated after female lampreys were treated with GTH, GnRHa (10 micrograms/lamprey) or GnRHa (1 microgram/lamprey) compared to controls. The present study is the first to demonstrate that the GnRH analogue stimulated in some way the pituitary-thyroid axis. These data suggest that a GnRH activity may activate both gonado- and thyrotropic secretion or that the endogenous hormone may itself have both functions in one of the most primitive vertebrates, the sea lamprey.

Animals↗
PubMed1985

The effects of estradiol and triiodothyronine on protein synthesis by hepatocytes of juvenile coho salmon (Oncorhynchus kisutch).

A method was developed for studying the in vitro metabolism of radiolabeled amino acids by dispersed salmon hepatocytes. Radioactivity accumulated in trichloroacetic acid (TCA)-precipitable and -soluble fractions of cells and in TCA-precipitable fractions of incubation medium was measured. Estradiol (E2) or triiodothyronine (T3) stimulated the amount of radioactivity in the TCA-precipitable fraction of cells in a dose-dependent manner. T3 caused an increase in TCA-soluble radioactivity of cells that were incubated with [14C]serine, [14C]glycine or the nonmetabolizable amino acid [14C]cycloleucine. E2 had either no effect or caused a decrease in TCA-soluble radioactivity in cells that were incubated with [14C]serine or [14C]glycine. E2 increased TCA-soluble radioactivity in cells that were incubated with [14C]cycloleucine. E2 but not T3 caused an increase in TCA-precipitable radioactivity in the medium from incubation of hepatocytes with metabolizable radioactive amino acids. These results suggest that protein metabolism by salmon hepatocytes is stimulated by both E2 and T3 with differing kinetic patterns.

Animals↗
PubMed1985

Corticotrophin-like bioactivity in the pituitary gland and brain of the pacific hagfish, Eptatretus stouti.

The cytochemical bioassay for corticotrophin (ACTH) was used in an attempt to detect ACTH-like activity in the Pacific hagfish, Eptatretus stouti. Extracts of the pituitary gland and brain were active in this assay system but those of liver and skeletal muscles were not. The slopes of the dose-response lines of the pituitary extracts were less than those of the mammalian corticotrophin standard preparation but greater than those of the brain extracts. The results suggest that the corticotrophic factor in the hagfish differs from mammalian ACTH.

Adrenal Glands↗
PubMed1985

Immunoreactivity for Met-enkephalin and substance P in cells of the adenohypophysis of larval and adult sea lampreys, Petromyzon marinus.

Procedures for localizing immunoreactive Met-enkephalin and substance P were applied to the adenohypophysis of larval and adult sea lamprey, Petromyzon marinus. Immunopositive reaction to anti-Met-enkephalin antiserum was found in certain adenohypophysial cells of both larvae and adults. This reaction was specific, as judged by preabsorption of the antiserum with synthetic Met-enkephalin and subsequent elimination of the immunoreaction. An immunopositive response to one of three anti-substance P antisera, also selective for certain adenohypophysial cells was obtained in both larval and adult glands. This reaction was not completely eliminated by preabsorption with authentic substance P. Although the substance P immunoreaction is not specific for authentic mammalian substance P, its localization is characteristic and distribution of cells exhibiting it is described. Immune-staining of Met-enkephalin was seen in most of the cells of the rostral pars distalis, and it was as strong or stronger in larvae (ammocoetes) of Petromyzon as it was in adults. The substance P response was found in about half of the cells of the caudal pars distalis and in a few cells of the rostral pars distalis. In ammocoetes substance P staining was limited to a few cells of the caudal pars distalis, and no cells in the rostral pars distalis were stained. Thus, Met-enkephalin staining in Petromyzon is a general property of cells in the rostral pars distalis both in larvae and adults and cannot be correlated with such events in the life cycle as metamorphosis or reproduction. On the other hand, cells containing materials reactive with the anti-substance P serum appear at a very low level in the larva and grow in number and intensity of staining in a time pattern that parallels development of reproductive capacity. Furthermore, the disparity in time of synthesis and adenohypophysial and cellular distribution of Met-enkephalin-like and substance P-like materials indicates that these two peptides are not functionally related, as has been suggested for some higher vertebrates.

Animals↗
PubMed1985

Changes in plasma steroid and thyroid hormones and insulin during final maturation and spawning of the sea lamprey, Petromyzon marinus.

Circulating levels of plasma estradiol-17 beta, androgens, thyroxine, triiodothyronine, immunoreactive insulin, plasma fatty acids, and protein were measured at interval during the period of final gonadal maturation, prior to spawning of male and female sea lampreys. Plasma estradiol levels fluctuated significantly and generally covaried in males and females through time. In females, possibly in relation to environmental changes, mean plasma estradiol levels peaked four times during the final spawning period but decreased sharply at the time of ovulation. In males, mean plasma estradiol peaked seven times during the final prespawning period and, in contrast to females, peaked significantly at the time of final spermiation. Plasma androgens were extremely low and covaried in males and females through time. Like plasma steroid profiles, there were coordinated changes in plasma triiodothyronine and thyroxine levels in males and females through the prespawning season. There was a slight increase in plasma insulin during the terminal maturation of the lampreys. However, at ovulation, the insulin levels abruptly decreased in females, whereas in males they remained unchanged. Plasma protein and fatty acid levels gradually decreased until ovulation/spermiation. At ovulation plasma fatty acid levels increased.

Androgens↗
PubMed1985

Characterization of coho salmon (Oncorhynchus kisutch) insulin.

Insulin has been isolated from islet tissue of coho salmon (Oncorhynchus kisutch) by gel filtration and HPLC and the complete amino acid sequence has been determined. The sequence differs from bovine insulin at 14 sites but all interchanges are conservative from the viewpoint of preservation of conformation. A comparison of insulin sequences from other fish is presented. Salmon insulin cross-reacts very weakly with antiserum to bovine insulin and vice versa. A completely homologous radioimmunoassay has been developed and used to estimate the insulin in salmon islet tissue and in plasma. The hypoglycemic effect of salmon insulin in salmon was more pronounced and persisted longer than that caused by identical doses of bovine insulin.

Amino Acid Sequence↗
PubMed1984

Changes in plasma estradiol and effects of triiodothyronine on plasma estradiol during smoltification of coho salmon, Oncorhynchus kisutch.

Plasma estradiol-17 beta levels were measured by radioimmunoassay in untreated coho salmon of both sexes or in fish fed triiodo-L-thyronine during the smoltification period. Mean plasma estradiol increased between February 25 and April 1 from 94 to 142 pg/ml, and then by May 13, it had decreased to 80 pg/ml. This hormonal cycle was followed by a second significant increase to 219 pg/ml on June 22. Plasma thyroxine level covaried with that of estradiol. Treatment with triiodothyronine had no effect on plasma estradiol or thyroxine levels. Plasma estradiol surges during the smoltification period must be considered along with other significant endocrine changes for a possible role in the developmental phenomena that characterize this period.

Animals↗
PubMed1984

Distribution of immunoreactive sites for several components of pro-opiocortin in the pituitary and brain of adult lampreys, Petromyzon marinus and Entosphenus tridentatus.

The occurrence and localization of molecular components of pro-opiocortin in the pituitary and brain of two species of adult lamprey, Petromyzon marinus and Entosphenus tridentatus, were studied immunocytochemically using antisera generated against human pro-gamma-MSH (N-terminal fragment 1Trp to 71Gly of pro-opiocortin), porcine ACTH, alpha-MSH, human beta-endorphin, gamma-endorphin, and methionine enkephalin. (1) In both species of lamprey most cells of the rostral pars distalis and some cells of the caudal pars distalis contained Met-enkephalin-like immunoreactivity. Some of these cells also contained gamma-endorphin-like immunoreactivity. After preabsorbing the antisera with their corresponding antigens or related peptides, the Met-enkephalin/gamma-endorphin-like material was found to be related to Met-enkephalin, but not identical with either Met-enkephalin or gamma-endorphin. However, results of anti-pro-gamma-MSH, anti-ACTH, anti-alpha-MSH, or anti-beta-endorphin were consistently negative in the pars distalis of both lamprey species. (2) Immunoreaction to anti-Met-enkephalin was found in some cells of the pars intermedia in both species of lamprey. Although the positive reaction had been eliminated by preabsorption with synthetic Met-enkephalin, the diffuseness of the positive stain in the pars intermedia cells resembled an artifactual cross-reaction rather than a specific reaction. In P. marinus, but not in E. tridentatus, similar inconsistent and questionable immunoreactions corresponding to ACTH and alpha-MSH also occurred in some pars intermedia cells. Results of other antisera (anti-pro-gamma-MSH, anti-beta-endorphin, or anti-gamma-endorphin) were consistently negative in the pars intermedia of both lamprey species. (3) In both species of lamprey beta-endorphin-like material was found in the hypothalamus. In E. tridentatus only Met-enkephalin-like material was observed in the hypothalamus, and these two substances were distributed in different neuronal elements. After application of anti-pro-gamma-MSH, anti-ACTH, anti-alpha-MSH, or anti-gamma-endorphin, no positive reaction was found in the brain of either species of lamprey. These findings suggest that if a pro-opiocortin-related prohormone exists in the lamprey, it may be chemically different from those of more advanced vertebrates, and it clearly differs in distribution between the brain and parts of the pituitary gland.

Adrenocorticotropic Hormone↗
PubMed1984

A study of triiodothyronine-catecholamine interactions: their effect on plasma fatty acids in Pacific hagfish Eptatretus stouti.

Plasma circulating levels of fatty acids (PFA) were measured in intact and in triiodothyronine (T3)-treated Pacific hagfish Eptatretus stouti. Intraperitoneal injection of both pharmacological (200 ng/g) and physiological (1 ng/g) doses of T3 caused an elevation of PFA 24 and 48 hr after treatment. The implantation of capsules containing the antithyroid compound, 6-propylthiouracil (6-PTU) decreased PFA levels. Twenty-four hr after T3-injection the norepinephrine (NE) content of plasma declined, whereas epinephrine (E) titres increased. Forty-eight hr after T3-treatment the mean titres of dopamine (D) and NE were lower than in the control group of hagfish. The treatment of hagfish with E in either pharmacological (2-3 micrograms/g) or physiological (2-3 ng/g) doses did not cause any elevation of PFA during the 72 hr following injection. In the same experiment the high dose of E induced long-lasting hyperglycemia, whereas the low dose had no substantial effect on glycemic levels. The data provide evidence that in hagfish, unlike in higher animals, the observed lipolytic effect of administered T3 is not mediated through the potentiation of the fat mobilizing action of catecholamines.

Animals↗
PubMed1984

The effect of insulin on amino acid metabolism and glycogen content in isolated liver cells of juvenile coho salmon, Oncorhynchus kisutch.

Amino acid transport and [14C]leucine incorporation into liver proteins as well as the secretion of proteins into incubation medium were studied in liver cells isolated from coho salmon (Oncorhynchus kisutch) parr. Pink salmon (Oncorhynchus gorbuscha) or mammalian (bovine) insulin caused a significant increase in TCA-precipitable radioactivity from both cells and incubation medium. The effects appeared at insulin concentration of 10(-8) M with a maximal response at 5 X 10(-8) M. The radioactivity of the TCA-soluble fraction was not changed by insulin. Insulin increased the amount of the non-metabolized amino acid [14C]cycloleucine, in the TCA-soluble fraction of hepatocytes. The glycogen content of hepatocytes was increased in the presence of insulin at 10(-9) M but was not changed from the control value in the presence of insulin at 10(-8) M.

Amino Acids↗
PubMed1983

Immunocytochemical localization of somatostatin and vasotocin in the brain of the Pacific hagfish, Eptatretus stouti.

The brain of the Pacific hagfish, Eptatretus stouti, was studied immunocytochemically using antisera against somatostatin (SRIH), arginine vasopressin (AVP), and adrenocorticotropic hormone (ACTH). SRIH-immunoreactive perikarya were distributed bilaterally in the postoptic nucleus and in the hypothalamic nucleus. Although several short, stained fibers were observed in the vicinity of the perikarya, SRIH-immunoreactivity was not found in the neurohypophysis, nor in other parts of the brain. On the other hand, presumed arginine vasotocin (AVT) perikarya were distributed in an arc-shaped region extending from the posterior part of the preoptic nucleus to the anterior-most end of the hypothalamic nucleus and projected their fibers to the neurohypophysis. Most presumptive AVT perikarya were located close to the paired prehypophysial arteries near the anterior end of the postoptic nucleus. In the neurohypophysis, abundant presumptive AVT-fibers terminated in the posterior dorsal wall, although some fibers terminated in the anterior dorsal wall and only a few fiber endings were found in the ventral wall. No ACTH-positive cells were detected in the hagfish brain or in the pituitary gland.

Adrenocorticotropic Hormone↗
PubMed1983

Plasma thyroid hormones in cyclostomes: do they have a role in regulation of glycemic levels?

Plasma levels of thyroxine (T4) and triiodothyronine (T3) were measured by radioimmunoassay in intact Pacific lamprey (Entosphenus tridentatus) undergoing the period of natural fasting and in Pacific hagfish (Eptatretus stouti) maintained unfed in the laboratory. Plasma T3 levels in both lamprey and hagfish were always severalfold lower than T4 levels. The influence of thyroid hormones on glycemic level was studied following intraperitoneal injection of T4 or T3 (13-20 micrograms/100 g body wt), as well as after implantation of sealed Silastic capsules containing the goitrogen, 6-propylthiouracil (6-PTU), or after intraperitoneal injections of an antithyroglobulin serum (ATgS) exhibiting both anti-T4 and anti-T3 activities. Measured plasma T4 and T3 levels after hormonal injection were extremely high and could be considered pharmacological. The 6-PTU treatment decreased plasma levels of both T4 and T3 within several weeks. The glycemic levels in lampreys and hagfish after thyroid hormone treatment were lower than in control animals, whereas in animals treated with either 6-PTU or ATgS, hyperglycemic levels prevailed. It is concluded that thyroid hormones, possibly acting with other hormones, may participate in the maintenance of glycemic levels in cyclostomes and that their action is to reduce glycemic levels.

Animals↗
PubMed1983

The effect of insulin insufficiency on plasma thyroid hormones and some metabolic constituents in Pacific hagfish, Eptatretus stouti.

The effect of guinea pig anti-human insulin serum was studied in Pacific hagfish. The metabolic indicators of insulin insufficiency, such as elevation of plasma glucose, free fatty acids, and alpha-amino nitrogen levels were obtained at 72 and 120 hr after anti-insulin serum injection. Plasma triiodothyronine levels declined significantly 24 hr after anti-insulin serum administration. These findings supplement earlier data with the same species and suggest that the regulatory metabolic action of insulin and thyroid hormones are related in cyclostomes.

Animals↗
PubMed1982

Comparison of thyroid hormone binding to heptic nuclei of the rat and a teleost (Oncorhynchus kisutch).

A modified T3 binding assay was used with coho salmon liver nuclei. Purified nuclei were incubated with [125I]T3 (or [125I]T4), nonradioactive thyroid hormone, or thyroid hormone analog. Bound hormone was separated from hormone by use of polyethylene glycol. Salmon liver nuclei specifically bound T3 with a high affinity [Ka = 1.031 +/- 0.174 x 10(9) M-1 (mean +/- SE); n = 12] which was 50% of the affinity measured with rat liver nuclei using the same assay. Salmon nuclear T3-binding capacity was 0.127 +/- 0.035 pmol T3/mg DNA (n = 7). Rat liver nuclear capacity for T3 binding was 3.4-fold greater than in salmon liver nuclei. T3 binding to salmon liver nuclei was greater than to nuclei from salmon brain; T3 binding to salmon spleen nuclei was low. Binding competition studies with hormone analogs indicated that binding to the salmon nuclei was dependent on molecular structure. These data indicate that the T3 binding to salmon nuclei may be due to T3 receptor activity. Analysis of Scatchard plots showed that the affinity of salmon hepatic nuclei for T3 is 10-fold greater than the affinity for T4. Reciprocal binding competition experiments with T3 and T4 indicate that both hormones bind to the same site. This suggests that in salmon, as in mammals, the liver nuclei predominantly bind thyroid hormones at T3-binding sites. Hepatic nuclei of human, rat, chick embryo, amphibian larva, and salmon have similar affinities for thyroid hormones and similar relative affinities for several thyroid hormone analogs, suggesting that the receptor molecule has been highly conserved during evolution.

Animals↗