Dopamine involvement in the regulation of gonadotropin secretion in coho salmon

1986 ◽  
Vol 64 (6) ◽  
pp. 1245-1248 ◽  
Author(s):  
Glen Van Der Kraak ◽  
Edward M. Donaldson ◽  
John P. Chang
Keyword(s):  
Body Weight ◽  
Coho Salmon ◽  
Effective Means ◽  
Rapid Onset ◽  
Minor Role ◽  
Gonadotropin Secretion ◽  
Luteinizing Hormone Releasing Hormone ◽  
Gonadotropin Release ◽  
A Minor ◽  
Magnitude Increase

The effects of intraperitoneal injections of [D-Ala6,Pro9-N-ethylamide]-luteinizing hormone-releasing hormone (LHRH-A) and pimozide, a dopamine receptor antagonist, on plasma gonadotropin levels and ovulation in coho salmon were investigated. Both LHRH-A (0.02 mg/kg body weight) and pimozide (10 mg/kg body weight) stimulate gonadotropin secretion, with LHRH-A causing a more rapid onset of gonadotropin release and a higher magnitude increase in plasma gonadotropin levels than pimozide. Pimozide caused a marked potentiation of the gonadotropin release response to LHRH-A. Injections of LHRH-A alone and in combination with pimozide were effective means of inducing ovulation, whereas pimozide alone was ineffective. These data support the concept that dopamine participates in the regulation of gonadotropin secretion in teleosts and suggest that dopamine has a minor role in the regulation of ovulatory gonadotropin changes in coho salmon compared with cyprinids.

Mifepristone (RU 486), a blocker of type II glucocorticoid and progestin receptors, reverses a dietary form of obesity

1992 ◽  
Vol 262 (6) ◽  
pp. R1106-R1110 ◽  
Author(s):  
S. Okada ◽  
D. A. York ◽  
G. A. Bray
Keyword(s):  
Body Weight ◽  
Glucocorticoid Receptors ◽  
Body Weight Gain ◽  
The Body ◽  
Receptor Activity ◽  
Minor Role ◽  
Type Ii ◽  
Fat Pad ◽  
Ru 486 ◽  
A Minor

The effect of mifepristone (RU 486), a blocker of type II glucocorticoid receptors on the development of obesity that follows the feeding of a high-fat (HF) diet to Osborne-Mendel (OM) rats, has been investigated. OM rats fed a HF diet gained more weight and had larger retroperitoneal and parametrial fat pads than OM rats fed a high-carbohydrate low-fat (LF) diet. RU 486 (30 mg.kg-1.day-1) for 14 days completely reversed the body weight gain and the increase in fat pad size of OM rats fed a HF diet. RU 486 had no effect on body weight of OM rats fed a LF diet, but did reduce fat pad weights. The data suggest that type II glucocorticoid receptor activity modulates body fat deposition and is essential for the development of obesity, although a minor role for progestin receptor activity cannot be ruled out.

Plasma gonadotropin, 17β-estradiol, and 17α,20β-dihydroxy-4-pregnen-3-one levels during luteinizing hormone-releasing hormone analogue and gonadotropin induced ovulation in coho salmon (Oncorhynchus kisutch)

1985 ◽  
Vol 63 (4) ◽  
pp. 824-833 ◽  
Author(s):  
Glen Van Der Kraak ◽  
Helen M. Dye ◽  
Edward M. Donaldson ◽  
George A. Hunter
Keyword(s):  
Luteinizing Hormone ◽  
Coho Salmon ◽  
Effective Means ◽  
Rate Of Change ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Induced Ovulation ◽  
Rate Of Increase ◽  
17Β Estradiol ◽  
Estradiol Levels

Intraperitoneal injections of des Gly10-(D-Ala6) luteinizing hormone-releasing hormone ethylamide (LH-RHA DAla6) alone and in combination with partially purified chinook salmon gonadotropin (SG-G100) were shown to be highly effective means of inducing ovulation in coho salmon. Two injections of LH-RHA DAla6 72 h apart or LH-RHA DAla6 injected with or 72 h following an injection of SG-G100 induced ovulation in 6–10 days. The induction of ovulation was associated with the duration rather than the initial magnitude of the increase in plasma gonadotropin levels. Plasma 17β-estradiol levels decreased whereas plasma 17α,20β-dihydroxy-4-pregnen-3-one (17α20βP) levels increased in response to elevated plasma gonadotropin levels. The time of ovulation was related to the magnitude and rate of change in plasma 17β-estradiol and 17α20βP levels. Ovulation occurred following a reduction of plasma 17β-estradiol levels to less than 2 ng/mL and this decline preceded or was concomitant with an increase in plasma 17αt20βP levels to 450–500 ng/mL. 17α20βP levels in fish which underwent oocyte maturation but not ovulation were lower (100 ng/mL), suggesting that high levels of 17α20βP may have a direct role in ovulation. Changes in 17β-estradiol production appear to determine the time of ovulation by influencing the magnitude and rate of increase of plasma 17α20βP levels.

scholarly journals No Evidence That RFamide-Related Peptide 3 Directly Modulates LH Secretion in the Ewe

Endocrinology ◽  
2016 ◽  
Vol 157 (4) ◽  
pp. 1566-1575 ◽  
Author(s):  
C. Decourt ◽  
K. Anger ◽  
V. Robert ◽  
D. Lomet ◽  
J. Bartzen-Sprauer ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Estradiol Benzoate ◽  
Inhibitory Effect ◽  
Minor Role ◽  
Gonadotropin Secretion ◽  
Related Peptide ◽  
Lh Pulsatility ◽  
Lh Release ◽  
A Minor ◽  
Lh Secretion

Abstract The neuropeptide RFamide-related peptide 3 (RFRP-3) has been implicated in the control of gonadotropin secretion in both birds and mammals. However, in mammals, depending on species, sex and photoperiod, inhibitory, excitatory, or no effect of RFRP-3 on the plasma concentration of LH has been reported. In the ewe, treatment with RFRP-3 either reduced LH concentration or had no effect, and treatment with an RFRP-3 receptor antagonist (ie, RF9) resulted in increased concentration of plasma LH. To clarify these conflicting results in the present study, a set of experiments was performed in ewes. Multiple iv injections of RFRP-3 (6 × 50 μg) in ovariectomized ewes had no effect on plasma LH pulsatility. In intact ewes a bolus injection (500 μg) or an injection (250, 500, or 1000 μg) followed by a 4-hour perfusion (250, 500, or 1000 μg · h−1) of RFRP-3 had no effect on the LH pulse induced by kisspeptin (6.5 μg). In ovariectomized, estrogen-replaced ewes, the LH surge induced by estradiol benzoate was not modified by a 24-hour perfusion of RFRP-3 (500 μg h−1). Finally, although treatment with RF9 induced a robust release of LH, treatment with a more selective RFRP-3 receptor antagonist, GJ14, resulted in no evident increase of LH. In contrast to the inhibitory effect previously suggested, our data are more consistent with the concept that RFRP-3 has no direct effect on LH secretion in ewes and that RF9 effect on LH release is likely not RFRP-3 receptor mediated. Hence, RFRP-3 probably has a minor role on the control of LH secretion in the ewe.

The effects of different doses of pimozide and [D-Ala6, Pro9-N ethylamide]-LHRH (LHRH-A) on gonadotropin release and ovulation in female goldfish

1985 ◽  
Vol 63 (6) ◽  
pp. 1252-1256 ◽  
Author(s):  
M. Sokolowska ◽  
R. E. Peter ◽  
C. S. Nahorniak
Keyword(s):  
Body Weight ◽  
Dopamine Antagonist ◽  
Dose Dependency ◽  
Maximum Serum ◽  
Luteinizing Hormone Releasing Hormone ◽  
Gonadotropin Release ◽  
Serum Gonadotropin ◽  
Dose Dependent ◽  
Late Stages ◽  
Different Doses

Female goldfish, in late stages of ovarian recrudescence, held at 12 or 20 °C, were injected with a range of dosages of the dopamine antagonist pimozide, at 10, 1, and 0.1 μg/g body weight, to block the endogenous gonadotropin release inhibitory activity of dopamine, and 3 h later were injected with [D-Ala6, Pro9-N ethylamide]-luteinizing hormone-releasing hormone (LHRH-A), at 0.1 μg/g body weight, after which serum gonadotropin levels were determined. The results demonstrate the dose dependency of pimozide in potentiating the activity of LHRH-A. In a second set of experiments, using female goldfish in a preovulatory condition, held at 12 and 20 °C, the changes in serum gonadotropin levels and frequency of ovulation were determined following injection of pimozide, at 1 μg/g body weight, and LHRH-A, at 0.1, 0.01, and 0.001 μg/g body weight. The results demonstrate that pimozide potentiates a dose-dependent response to LHRH-A. The maximum serum GtH levels found in response to the same dosages of pimozide and LHRH-A at 12 and 20 °C were similar; however, the maximum levels occurred earlier at 20 °C (6 h postinjections) than at 12 °C (24 h postinjections). Notably, only the combination of pimozide at 1 μg/g body weight and LHRH-A at 0.1 μg/g body weight, in fish at 20 °C, was highly effective in inducing ovulation.

The Effect of Path Length and Display Size on Memory for Spatial Information

2012 ◽  
Vol 59 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Katherine Guérard ◽  
Sébastien Tremblay
Keyword(s):  
Path Length ◽  
Potential Role ◽  
Spatial Information ◽  
Recall Performance ◽  
Minor Role ◽  
Length Effect ◽  
Serial Memory ◽  
Fixed Reference ◽  
A Minor

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

Use of Different Tissue Thromboplastins in the Control of Anticoagulant-Therapy

1958 ◽  
Vol 02 (05/06) ◽  
pp. 462-480 ◽  
Author(s):  
Marc Verstraete ◽  
Patricia A. Clark ◽  
Irving S. Wright
Keyword(s):  
Prothrombin Time ◽  
Anticoagulant Therapy ◽  
Factor Vii ◽  
Rabbit Brain ◽  
Minor Role ◽  
Rabbit Lung ◽  
Coagulation Mechanism ◽  
Time Test ◽  
The One ◽  
A Minor

SummaryAn analysis of the results of prothrombin time tests with different types of thromboplastins sheds some light on the problem why the administration of coumarin is difficult to standardize in different centers. Our present ideas on the subject, based on experimental data may be summarized as follows.Several factors of the clotting mechanism are influenced by coumarin derivatives. The action of some of these factors is by-passed in the 1-stage prothrombin time test. The decrease of the prothrombin and factor VII levels may be evaluated in the 1-stage prothrombin time determination (Quick-test). The prolongation of the prothrombin times are, however, predominantly due to the decrease of factor VII activity, the prothrombin content remaining around 50 per cent of normal during an adequate anticoagulant therapy. It is unlikely that this degree of depression of prothrombin is of major significance in interfering with the coagulation mechanism in the protection against thromboembolism. It may, however, play a minor role, which has yet to be evaluated quantitatively. An exact evaluation of factor VII is, therefore, important for the guidance of anticoagulant therapy and the method of choice is the one which is most sensitive to changes in factor VII concentration. The 1-stage prothrombin time test with a rabbit lung thromboplastin seems the most suitable method because rabbit brain preparations exhibit a factor VII-like activity that is not present in rabbit lung preparations.

Produktivkraft als Versprechen

2016 ◽  
Vol 46 (185) ◽  
pp. 621-638 ◽  
Author(s):  
Christian Siefkes
Keyword(s):  
Private Consumption ◽  
Minor Role ◽  
Progressive Reduction ◽  
Internal Forces ◽  
A Minor

The ‘Fragment on Machines’ from Marx’s Grundrisse is often cited as an argument that the internal forces of capitalism will lead to its doom. But the argument that the progressive reduction of labor must doom capitalism lacks a proper foundation, as a comparison with the ‘Schemes of Reproduction’ given in Capital II shows. The latter, however, aren’t fully convincing either. In reality, more depends on the private consumption of capitalists than either model recognizes. Ultimately, most can be made of the ‘Fragment on Machines’ by reading it not as an exposure of capitalism’s internal contractions, but as a discussion of a possible communist future where labor (or work) will play but a minor role.

INFLUENCE OF METYRAPONE ON PLASMA CONCENTRATIONS OF TESTOSTERONE AND ANDROSTENEDIONE IN MAN

1971 ◽  
Vol 68 (3) ◽  
pp. 576-584 ◽  
Author(s):  
K. O. Nilsson ◽  
B. Hökfelt
Keyword(s):  
Body Weight ◽  
Male Patient ◽  
Gradual Increase ◽  
Plasma Concentrations ◽  
Plasma Testosterone ◽  
Testosterone Levels ◽  
Basal Plasma ◽  
Normal Males ◽  
A Minor ◽  
Secondary Hypogonadism

ABSTRACT Metyrapone was administered either orally, 750 mg every four h, in a total of six doses, or intravenously 30 mg per kg body weight as a four h infusion. In three males with normal endocrine functions, metyrapone given orally or intravenously induced a fall in plasma testosterone and an elevation of androstenedione within 2–8 h. When metyrapone was administered to a patient given dexamethasone to suppress endogenous ACTH production, the androstenedione levels did not alter whereas the testosterone levels showed a slight, transient decrease. In two normal females metyrapone administration was followed by a marked increase in plasma androstenedione whereas testosterone showed only a minor, gradual increase. In one male patient with Addison's disease the basal plasma testosterone was normal whereas the level of androstenedione was low. Following metyrapone intravenously, there was a slight suppression of plasma testosterone but no change in the androstenedione concentration. In one patient with primary hypogonadism, two with secondary hypogonadism and two with Klinefelter's syndrome the plasma testosterone was low under basal conditions and did not change following metyrapone. Basal plasma androstenedione was within the range for normal males and increased markedly following metyrapone in all the cases.

Effects of Myo-inositol Alone and in Combination with Seleno-Lmethionine on Cadmium-Induced Testicular Damage in Mice

2019 ◽  
Vol 12 (4) ◽  
pp. 311-323 ◽  
Author(s):  
Salvatore Benvenga ◽  
Antonio Micali ◽  
Giovanni Pallio ◽  
Roberto Vita ◽  
Consuelo Malta ◽  
...  
Keyword(s):  
Structural Changes ◽  
Natural Antioxidants ◽  
Minor Role ◽  
Positive Role ◽  
Testosterone Levels ◽  
Tnf Α ◽  
Testicular Lesions ◽  
A Minor ◽  
Immunohistochemical Analyses

Background: Cadmium (Cd) impairs gametogenesis and damages the blood-testis barrier. Objective: As the primary mechanism of Cd-induced damage is oxidative stress, the effects of two natural antioxidants, myo-inositol (MI) and seleno-L-methionine (Se), were evaluated in mice testes. Methods: Eighty-four male C57 BL/6J mice were divided into twelve groups: 0.9% NaCl (vehicle; 1 ml/kg/day i.p.); Se (0.2 mg/kg/day per os); Se (0.4 mg/kg/day per os); MI (360 mg/kg/day per os); MI plus Se (0.2 mg/kg/day); MI plus Se (0.4 mg/kg/day); CdCl2 (2 mg/kg/day i.p.) plus vehicle; CdCl2 plus MI; CdCl2 plus Se (0.2 mg/kg/day); CdCl2 plus Se (0.4 mg/kg/day); CdCl2 plus MI plus Se (0.2 mg/kg/day); and CdCl2 plus MI plus Se (0.4 mg/kg/day). After 14 days, testes were processed for biochemical, structural and immunohistochemical analyses. Results: CdCl2 increased iNOS and TNF-α expression and Malondialdehyde (MDA) levels, lowered glutathione (GSH) and testosterone, induced testicular lesions, and almost eliminated claudin-11 immunoreactivity. Se administration at 0.2 or 0.4 mg/kg significantly reduced iNOS and TNF-α expression, maintained GSH, MDA and testosterone levels, structural changes and low claudin-11 immunoreactivity. MI alone or associated with Se at 0.2 or 0.4 mg/kg significantly reduced iNOS and TNF-α expression and MDA levels, increased GSH and testosterone levels, ameliorated structural organization and increased claudin-11 patches number. Conclusion: We demonstrated a protective effect of MI, a minor role of Se and an evident positive role of the association between MI and Se on Cd-induced damages of the testis. MI alone or associated with Se might protect testes in subjects exposed to toxicants, at least to those with behavior similar to Cd.

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