V.L. de Vlaming

Estradiol-17β effects on lipid and carbohydrate metabolism and on the induction of a yolk precursor in goldfish, CarassiusAuratus

Abstract The effects of estradiol-17β treatment on plasma lipid levels, liver lipid and glycogen reserves were examined during different phases of the reproductive cycle in goldfish, Carassius auratus . Estrogen therapy resulted in increased plasma and hepatic lipid levels except during the spawning season. Hepatic glycogen deposits were depleted by estradiol injections during all seasons. Treatment of fish with the estrogen antagonist, CI-628, during the spawning season caused a reduction in plasma and liver lipid levels. Electrophoretic studies conducted during the post-spawning season showed that estrogen induces the appearance of a specific lipoprotein, probably a yolk precursor, in the serum and liver of goldfish.

Photoperiod effects on hypothalamic serotonergic activity in the goldfish, Carassius auratus

Abstract 1. 1. The nature of hypothalamic serotonergic activity in goldfish exposed to various photo-period regimes was examined for day -night differences. 2. 2. Fish maintained throughout the course of these experiments on a short photoperiod (8L/16D, 20°C) showed no day-night differences in hypothalamic serotonin content or in serotonergic activity. 3. 3. Fish transferred from the short photoperiod to a long photoperiod (16L/8D, 20°C) developed day-night differences in hypothalamic serotonin content within 72 h, while day night differences in hypothalamic serotonergic activity were observed after 2 weeks. 4. 4. Data presented suggest that hypothalamic serotonergic mechanisms play a role in mediating the effects of photoperiod on physiological processes in goldfish.

The effects of mammalian prolactin and growth hormone on goldfish (Carassius auratus) growth, plasma amino acid levels and liver amino acid uptake

Abstract 1. 1. The effects of ovine prolactin (oPRL) and bovine growth hormone (bGH) on goldfish (Carassius auratus) growth and amino acid metabolism were examined. 2. 2. Linear growth was accelerated by bGH treatment; oPRL had a suggestive, but not significant, effect. 3. 3. Plasma amino acid levels were consistently lower in fish treated with oPRL and maintained at temperatures between 15–20°C. In only one of three experiments were plasma amino acid levels lowered by bGH administration. 4. 4. In vitro incorporation of [14C]glycine into liver protein was accelerated by oPRL. but not bGH.

Effects of inhibitors on monoamine oxidase activity in perch (Perca flavescens) brain in vitro

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.

Interaction of environmental photoperiod and temperature on hypothalamic monoamine oxidase activity in Carassius auratus L.

Abstract 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.

Effects of para-chlorophenylalanine, a brain serotonin depletor, on pituitary cyclic AMP levels in the rainbow trout, Salmo gairdneri.

Abstract The tryptophan hydroxylase inhibitor para -chlorophenylalanine (pCPA) was employed in an investigation of the role of brain serotonin in the regulation of pituitary cyclic AMP levels in Salmo gairdneri . Hypothalamic serotonin content was measured with a fluorometric assay, while pituitary cAMP was determined by means of a double-antibody radioimmunoassay. A time-course study revealed that 250 mg pCPA/kg significantly reduced hypothalamic serotonin content within 1 hr after injection. Lower doses were effective in reducing serotonin content after 48 hr. Pituitary cAMP levels declined significantly 1 hr after injection of 250 mg pCPA/kg. Administration of pCPA at 50 and 250 mg/kg doses reduced cAMP levels within 24 hr. These data indicate that a serotonergic mechanism is involved with the regulation of pituitary cyclic AMP levels in the rainbow trout.

Photoperiod-temperature interactions on liver and plasma metabolites in the goldfish, Carassius auratus

Abstract 1. 1. Plasma and liver metabolites were measured in goldfish after 3 weeks acclimation to one of four different photoperiod-temperature regimes (16L/8D-22°C; 16L/8D-13°C; 8L/16D-22°C; 8L/16D-13°C) during September and April. Samples were taken at the mid-light and mid-dark point of each photoregime. 2. 2. Photoperiod altered levels of plasma protein and plasma cholesterol. 3. 3. Temperature affected the levels of liver glycogen, plasma glucose, organic bound phosphorus and protein. 4. 4. Time of sampling was important in assessing both photoperiod and temperature effects on metabolites. 5. 5. Interaction between photoperiod and temperature was observed in the levels of liver glycogen and plasma glucose. The interaction was dependent on sampling time. 6. 6. Seasonal differences were noted in the day-night variation of specific metabolites and of the photoperiod effects on plasma cholesterol levels.

Effects of photoperiod on plasma corticoid levels in the goldfish, Carassius auratus—role of the pineal

Abstract 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.

Seasonal effects of prolactin on aspects of carbohydrate and lipid metabolism in the goldfish, Carassius auratus

Abstract 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.