Victor L. de Vlaming

Goldfish (Carassius auratus) vitellogenin: Induction, isolation, properties and relationship to yolk proteins☆

Abstract 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.

Effects of pinealectomy on gonadal activity in the cyprinid teleost, Notemigonus crysoleucas ☆

Abstract Investigations were initiated to examine the effects of pinealectomy on gonadal activity in the cyprinid teleost, Notemigonus crysoleucas, during different phases of the reproductive cycle and maintained under different photoperiod-temperature regimes. The effects of pinealectomy varied depending on the phase of the natural reproductive cycle when the organ was removed, as well as, with the photoperiod-temperature regime under which the experimental animals were maintained. Pinealectomy causes testicular regression during the gonadal preparatory and prespawning season and retards final testicular maturation during the spawning season in fish maintained on a long photoperiod-warm temperature regime. Under these conditions epiphysectomy retarded ovarian development or caused ovarian involution during all phases of the gonadal maturation cycle. In Notemigonus maintained on a long photoperiod-low temperature regime, pinealectomy had no apparent effects on gonadal development during the preparatory and spawning seasons. During the prespawning season pinealectomy repressed ovarian development and caused testicular regression in fish exposed to a long photoperiod-low temperature regime. During the prespawning and spawning seasons pinealectomy stimulated gonadal activity in fish maintained on a short photoperiod-warm temperature regime. Under these same conditions epiphysectomy failed to alter gonadal activity during the gonadal preparatory season. No obvious changes could be detected in gonadal activity in pinealectomized fish exposed to short photoperiodlow temperature regimes during any phase of the gonadal maturation cycle. These data suggest that the pineal in Notemigonus may be either stimulatory or inhibitory to gonadal development depending on the photoperiod-temperature regime to which the fish are exposed.

Diurnal variations in the physiology of the goldfish, Carassius auratus

Abstract Liver glycogen, liver lipid, liver triglycerides, plasma glucose, plasma total lipid, plasma cholesterol, plasma corticoids, hypothalamic serotonin and pituitary pro‐lactin levels were assayed at five times over a 24‐h period in Carassius auratus maintained under a specific photoperiod regime at various times throughout the year. Diurnal variations were observed in all parameters monitored. Daily variations of liver glycogen, plasma glucose, plasma lipid, plasma corticoids and hypothalamic serotonin were affected by time of feeding. Liver glycogen, plasma lipid and plasma corticoid levels were also affected by time of feeding. Diurnal variations of liver glycogen, plasma glucose and plasma lipid were influenced by light‐dark cycles. These data illustrate that feeding time, photoperiod and time of sacrifice are important considerations in the study of metabolic and hormonal parameters in fishes.

The effects of melatonin treatment on gonosomatic index in the teleost, Fundulus similis, and the tree frog, Hyla cinerea

Melatonin-treated Fundulus similis collected in January or May and maintained on a long photoperiod had significantly smaller gonads than control animals. The effect of melatonin was independent of the time of day that it was administered. Melatonin treatment of F. similis maintained on a short photoperiod in May retarded testicular enlargement; melatonin treatment of animals on a short photoperiod in January was without effect. The gonadal enlargement seen in control Hyla cinerea maintained on a long photoperiod in December was inhibited by melatonin.

Effects of pinealectomy and melatonin treatment on liver and plasma metabolites in the goldfish, Carassius auratus

Abstract The effects of pineal removal on daily variations and levels of some liver and plasma metabolites were examined in the goldfish, Carassius auratus . Pinealectomy abolishes the liver glycogen daily variation and decreases hepatic glycogen levels in goldfish maintained on specific photoperiod regimes during spring and summer. Neither the daily variation nor the levels of hepatic glycogen are affected by pinealectomy during the fall. Pinealectomy alters the plasma glucose daily variation and increases the levels of this metabolite in fishes maintained on long photoperiods during the summer. During the fall the daily variation of plasma glucose is abolished by pinealectomy and blood sugar levels are decreased. The diurnal fluctuation of plasma lipid is altered by pinealectomy during the summer. Plasma lipid levels are elevated in pinealectomized fishes during winter, spring, and summer. The daily variation of liver lipid levels is altered by pinealectomy during the autumn. Melatonin treatment increases liver glycogen reserves in goldfish maintained on a long, but not a short, photoperiod during the spring. Plasma glucose levels are also elevated by melatonin treatment. Therefore, the pineal organ participates in regulating levels and daily variations of some metabolites. The influence of the pineal on metabolites varies with season and day length.

The effects of melatonin on lipid deposition in cyprinodontid fishes and on pituitary prolactin activity inFundulus similis

SummaryThe effect of melatonin treatment on lipid deposition inFundulus similis andCyprinodon variegatus was examined. Melatonin administration stimulates depletion of lipids inFundulus andCyprinodon acclimated to a long photoperiod; the action of this indolamine on lipid metabolism is independent of injection time inFundulus, but not inCyprinodon. Treatment ofFundulus with melatonin also causes a decrease in body fat in May when animals are maintained on a short photoperiod. However, an increase in lipids was observed inFundulus acclimated to a short photoperiod in July and treated with melatonin. These data suggest that the effects of melatonin on lipid deposition may depend on season and photoperiod conditions. Pituitary prolactin activity is reduced inFundulus treated with melatonin. The possibility that prolactin mediates the effects of melatonin on lipid metabolism is discussed.

Hypothalamic monoamine oxidase, a component in the serotonergic control of pituitary prolactin content in Carassius auratus L.

Abstract 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.

The effects of light reception on circulating estrogen levels in female goldfish, Carassius auratus: Importance of retinal pathways versus the pineal ☆

Abstract The effects of pinealectomy, optic tract section, or exposure to continuous darkness on serum estradiol-17β levels in the goldfish were examined during the spring and fall. Pineal removal had no effect on serum estrogen levels or GSI in either fall or spring. Optic tract section decreased serum estrogen levels in both spring and fall experiments. Ovarian regression was initiated in fish exposed to continuous darkness and optic tract-sectioned fish during the spring, but fish maintained in darkness exhibited no change in serum estrogen levels. Our data imply that it is primarily retinal pathways which mediate the effects of increasing daylength on goldfish ovarian development during the spring.

In vitro effects of insulin on liver lipid and carbohydrate metabolism in the teleost, Notemigonus crysoleucas.

Abstract 1. 1. The effects of mammalian insulin on in vitro liver carbohydrate and lipid metabolism in the cyprinid teleost, Notemigonus crysoleucas , were examined. 2. 2. Time course studies showed that the effects of insulin on liver lipid metabolism can be observed after 2 hr of incubation at 12°C and after 4 hr at 25°C. 3. 3. Insulin promotes lipogenesis in liver slices of Notemigonus at 12 and 25°C. A dose response was noted at 12°C, but not at 25°C. 4. 4. Glycogen deposition is stimulated in liver slices incubated with insulin at 12 and 25°C; the effects of the hormone are dose dependent at 12°C. 5. 5. Liver glycogen and lipid deposition occur in fish acclimated to 12°C, but in fish acclimated to 25°C both glycogen and lipid reserves are depleted from the liver. The effects of insulin on liver carbohydrate and lipid metabolism at 12 and 25°C appear to be quantitatively rather than qualitatively different.

Characteristics of monoamine oxidase activity in the hypothalamus of Carassius auratus as assayed by a fluorometric technique

Abstract 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. 2. Product formation (4-hydroxyquinoline) was found to be linear with respect to both time and homogenate volume. 3. The Michaelis constant for the enzyme was determined to be 4.5 × 10 −5 M for fish maintained on a 16L/8D, 11°C regime. 4. Pargyline, a common MAO inhibitor, dramatically reduced MAO activity at doses of 10 and 50 ng per incubation volume (1.75 ml). 5. Monoamine oxidase activity, when assayed at several incubation temperatures, did not depend on the acclimation temperature of the fish. The Q 10 for MAO activity was determined to be 2.0 for both acclimation groups.