The antiestrogen, clomiphene citrate ( Merrell -National Laboratories) was administered to female goldfish in order to test the hypothesis that this drug may act on brain monoaminergic mechanisms. Brain monoamine oxidase (MAO) activity and hypothalamic serotonin (5-HT) content were measured fluorometrically after i.p. administration of 0, 5 or 25 micrograms clomiphene citrate/g body wt. Brain MAO activity was significantly inhibited by the high dose of clomiphene citrate, whereas hypothalamic 5-HT content was significantly elevated by both low and high doses of the antiestrogen. These data support the idea that brain monoamines in teleost fish are influenced by estrogen feedback mechanisms which can be blocked by clomiphene citrate.

1. Perch brain homogenates were incubated in vitro and monoamine oxidase (MAO) activity was determined fluorometrically, using a kynuramine substrate. 2. Clorgyline, harmaline and deprenyl inhibited MAO activity in a concentration-related manner, with single sigmoid inhibition curves, and the type A inhibitors harmaline and clorgyline were more effective than the type B inhibitor deprenyl. 3. Two types of inhibition were recognized in vitro; a fast-onsetting inhibition, similar to that produced by a reversible inhibitor, and a slow-onsetting inhibition, which is time- and concentration-dependent and presumably represents inactivation of the enzyme.

1.1. Day-night variations of hypothalamic serotonergic activity were noted in goldfish maintained on a 16L/8D, 20°C regime but were not found in fish kept on an 8L/16D, 20°C regime.2.2. Pinealectomy had a significant effect on hypothalamic serotonin content and serotonergic activity in fish exposed to the long, but not short, photoperiod.3.3. Melatonin administration to control animals (100 μg per day for 10 days) modified the day-night variations of hypothalamic serotonin content and serotonergic activity regardless of photoperiod.4.4. The effects of melatonin on hypothalamic serotonin content in pinealectomized animals were dependent upon the photoperiod regime, whereas effects on serotonergic activity were not.5.5. It is concluded that the goldfish pineal organ and melatonin may play a role in hypothalamic adjustments to changing photoperiods.

1.1. Goldfish brain homogenates were incubated in vitro and monoamine oxidase (MAO) activity determined fluorometrically.2.2. Harmaline, clorgyline, deprenyl and pargyline inhibited MAO activity in a concentration-related manner with single-sigmoid inhibition curves. MAO was more sensitive to inhibition by type A MAO inhibitors than by a type B MAO inhibitor.3.3. Goldfish brain apparently contains only a single form of MAO, similar to mammalian type A MAO.4.4. The irreversible MAO inhibitor pargyline showed a fast-onsetting inhibition, similar to that of reversible inhibitors and a slow-onseting inhibition, time- and concentration-dependent, apparently related to the inactivation of the enzyme.

1.1. The effects of photoperiod and pinealectomy on plasma corticoid levels in the goldfish (Carassius auratus) were examined.2.2. Plasma corticoid levels differed in goldfish maintained under different photoperiod regimes, but this response varied seasonally.3.3. Pinealectomy altered the effects of photoperiod on plasma corticoid levels but this effect varied with season.4.4. Plasma corticoid levels were correlated with ovarian activity. The effects of photoperiod on plasma corticoid levels appear to be related to the influence of light on reproduction.5.5. The alteration of plasma corticoid levels in pinealectomized fish may be due to the role this organ plays in mediating photoperiod effects on gonadal activity.

1.1. Diurnal and seasonal variations of certain aspects of carbohydrate and lipid metabolism to ovine prolactin (PRL) treatment in the goldfish, Carassius auratus, were examined.2.2. PRL treatment late in the light phase of a long photoperiod during spring depletes liver glycogen stores. During fall liver glycogen levels are not affected by PRL treatment in fishes acclimated to long or short photoperiods. PRL is hypoglycaemic in fall and spring.3.3. PRL administered late in the light phase of a long photoperiod during spring increases plasma and liver total lipids and plasma cholesterol, while decreasing plasma triglycerides. In fall PRL may increase or decrease plasma organic-bound P levels dependent upon injection time.

1.1. The nature of photoperiod and temperature interactions on the level of hypothalamic monoamine oxidase activity in the goldfish was examined.2.2. Exposure of goldfish to long photoperiods (16L/8D) significantly elevated enzyme activity above that found in fish exposed to shorter photoperiods, but only when animals were kept at 20–22°C. No photoperiod effects were found in the case of animals maintained at 13°C however.3.3. Low temperatures (13°C) were effective in depressing hypothalamic monoamine oxidase activity, as compared to 22°C-acclimated fish, only when animals were maintained under a 16L/8D photoperiod.4.4. These data suggest that hypothalamic monoamine oxidase is regulated not simply by temperature or photoperiod acting independently, but by the interaction of these two factors.

1.1. A chromatographic procedure for isolating intact, highly purified vitellogenin from the plasma of the goldfish, Carassius auratus, is described.2.2. Vitellogenin is normally present in the plasma of females during the breeding season, but is not found in males; however, estradiol-17β induces the appearance of vitellogenin in male plasma.3.3. Native (dimeric_ goldfish vitellogenin has a molecular weight of about 380,000 and contains 15.4% protein-nitrogen and 0.79% protein-phosphorus; amino acid profiles were compared for vitellogenins from goldfish, Salmo gairdneri and Xenopus laevis.4.4. At least three polypeptides, ranging in molecular weight from 140,000 to 147,000, were identified by sodium dodecyl sulfate-gel electrophoresis of vitellogenin; native (dimeric) vitellogen is comprised of two such polypeptides together with approx 20% lipid.5.5. Native goldfish yolk protein consists of a lipovitellin and a phosvitin fraction; the former yields one class of at least two large polypeptides (mol. wt = 105,000 and 110,000) and another class of up to four small polypeptides (mol. wt = 19,000–25,000) on sodium dodecyl sulfate-gel electrophoresis, while the phosvitin fraction yields at least two polypeptides (mol. wt = 7600 and 14,500) on Sephadex-gel filtration.6.6. In this teleostean species, multiple vitellogenin polypeptides are apparently processed into multiple yolk protein polypeptides within the growing oocyte.

The relationships of ovary weight, liver weight and visceral lipid stores to body weight in the goldfish were examined at different times of the year. Both arithmetic and logarithmic relationships were examined. Ovary weight significantly increased relative to increasing body weight in goldfish and the exact nature of this relationship changed from month to month. However, larger fish were found to have proportionately larger ovaries than small fish at specific times of the year. Regression lines for liver weight versus body weight were also determined. Monthly differences were found in the liver weight‐body weight relationship. Visceral lipid stores expressed per gram of protein were found to be independent of body weight. Lipid stores expressed in this manner peaked in February while ovary weight peaked in April. The consequences of compensating for body size when expressing organ (liver, ovary) sizes, such as hepatosomatic index and gonosomatic index, are discussed.

The role of the enzyme monoamine oxidase (MAO) was examined with regard to the control of pituitary prolactin content in the goldfish. Inhibition of MAO by means of intraperitoneal injection of pargyline resulted in significantly elevated brain serotonin content. Concomitantly, pituitary prolactin stores were also significantly elevated. Time-course and dose-response experiments revealed that pargyline at doses ≥25 mg/kg completely inhibited MAO and significantly increased brain serotonin and pituitary prolactin content within 12 hr. It is concluded that the enzyme MAO may be a significant component of the monoaminergic system of the goldfish, serving to modulate the serotonergic inputs to centers involved in the control of pituitary prolactin secretion.

1. A fluorometric assay using kynuramine as a substrate for monoamine oxidase (MAO) activity in the basal medial lobe of the goldfish hypothalamus was verified.

Seasonal variations in reproductive condition and fat content of cyprinodontids from eight populations in Florida and southern Texas were examined. In all species the spawning period is protracted. Cyprinodon variegatus may spawn throughout the year. Spawning in Fundulus similis apparently occurs during all months except November, December, and January, but is terminated during September in F. grandis. Cessation of spawning occurs during September in F. lineolatus, but during July in F. chrysotus. Adinia xenica may have a longer spawning season than the species of the Fundulus investigated. A seasonal variation in body fat content was observed in C. variegatus, A. xenica, F. grandis, F. lineolatus, and F. similis (from Texas, but not Florida). Maximum fat reserves and the seasonal variation in fat levels differed among the species studied. Seasonal variations in body fat content and gonadal size were not correlated in any of the species. Seasonal changes in standing crops of zooplankton and phytoplankton were compared to annual variations of body fat content and gonadal size in C. variegatus and F. similis from Texas. Neither gonadal size nor fat content correlated with zooplankton or phytoplankton standing crops.

The effects of pinealectomy on pituitary and plasma gonadotropin levels and gonadal development in female goldfish exposed to various photoperiod‐temperature regimes during different seasons were examined. Pinealectomy during autumn had no effect on either pituitary or plasma hormone levels or gonadal development. When goldfish are pinealectomized in spring and exposed to long photoperiod conditions, the ovaries regress and plasma gonadotropin levels are significantly depressed compared to sham operated animals. Sham operated goldfish exposed to short photoperiod conditions in spring had regressing ovaries whereas pinealectomized animals under this regime either spawned or had ovaries in the late vitellogenic phase. Plasma gonadotropin titres in the pinealectomized group were significantly lower than those of sham operated animals. The pineal can be either stimulatory or inhibitory to gonadal development depending on the photoperiod regime to which the animals are exposed. The pineal apparently influences gonadal activity by modulating gonadotropin secretion. A diurnal variation in plasma gonadotropin levels was also observed in both sham operated and pinealectomized goldfish exposed to a long photoperiod warm‐temperature regime in spring.

A microelectrophoretic polyacrylamide slab gel system has been adapted to analyze prolactin levels in individual goldfish pituitaries. The putative prolactin (Rf = 0.40) was identified within the gels by use of what is known about hypothalamic, dopaminergic control of secretion of this hormone, the effect of osmotic pressure on prolactin secretion, and the effect of administration of ergot drugs in fish. The putative goldfish prolactin was also shown to cross-react with anti-ovine and anti-pollack prolactin in two systems.

Pinealectomy has an influence on pituitary prolactin levels in goldfish maintained under certain photoperiod-temperature regimes. The effects of pinealectomy on pituitary prolactin content depend on photoperiod and time of sampling. Thus, differences between pinealectomized and sham operated animals may be due to a shift of a daily variation in pituitary prolactin levels. The pineal in fishes may thus be involved in photoperiod influences on daily prolactin rhythms.

Diurnal variations in pituitary gonadotropin content were determined in the golden shiner, Notemigonus crysoleucas. In fish maintained on a 15‐5L/8‐5D–15°C regime, a pronounced circadian variation in pituitary gonadotropin potency was observed, the gonadotropin content being minimal early and maximal late during the light phase. Little temporal variation was seen in fish exposed to a 9L/15D–15°C regime. The effects of gonadotropin and prolactin treatment on gonadal activity in N. crysoleucas were also investigated. Salmon gonadotropin was effective in stimulating an increased rate of gonadal development when given early during the light phase in fish maintained on a 15.5L/8‐5D–15°C regime; injections of gonadotropin given late in the light phase failed to accelerate gonadal growth. Regardless of time of injection, ovine luteinizing hormone accelerated gonadal growth in fish maintained on a 9L/15D–15°C regime. Ovine prolactin retarded gonadal development in fish exposed to a 15.5L/8‐5D–24°C regime, independent of injection time. In fish maintained on a 15.5L/8‐5D–15°C regime, injections of prolactin given early, but not late, during the light phase repressed gonadal maturation. These data show that under certain photoperiod‐temperature conditions there is a temporal aspect to responsiveness to exogenous hormone treatment.