Mary Jo Vodicnik

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.

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.

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.

The effects of blinding, pinealectomy and exposure to constant dark conditions on gonadal activity in the female goldfish, Carassius auratus

SynopsisThe effects of pinealectomy, blinding, and exposure to constant darkness were examined in female goldfish during different seasons. Neither blinding nor pinealectomy under short or decreasing photoperiod conditions, nor exposure to constant darkness had an effect on ovarian activity in goldfish during fall and winter. In spring, constant darkness has an inhibitory effect on ovarian activity. Pinealectomy under increasing photoperiod conditions partially inhibits reproductive activity, but not to the extent of constant darkness. Blinding, under the same regime also inhibited to some extent the ovarian response to increasing photoperiod. Our data suggest that retinal pathways and the pineal organ are involved in the photosexual response to increasing day lengths.

Microelectrophoretic identification of pituitary prolactin in Carassius auratus

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.

Effects of photoperiod-temperature regimes on pituitary gonadotrophs, pituitary gonadotropin potency and hypothalamic gonadotropin releasing acitivity in the teleost notemigonus crysoleucas

Abstract 1. 1.|The effects of various photoperiod-temperature regimes on gonadal activity, hypothalamic gonadotropin releasing activity, pituitary gonadotropin potency and pituitary gonadotrophs were examined in the teleost, Notemigonus crysoleucas . 2. 2.|In fish maintained on a long photoperiod-high temperature regime final gonadal maturation occurs. Under these conditions hypothalamic gonadotropin releasing activity is high, stainable gonadotrophs make up a low percentage of pituitary area and pituitary gonadotropin potency is relatively low. 3. 3.|Gonadotrophs make up a relatively large area of the pituitary and adenohypophyseal gonadotropin activity is high in fish exposed to long photoperiod-low temperature regimes. Long photoperiod-low temperature regimes do not stimulate final gonadal maturation. 4. 4.|Short photoperiod-high temperature conditions retard gonadal development or cause gonadal regression in Notemigonus . The area of the pituitary occupied by gonadotrophs and hypothalamic gonadotropin releasing activity are low in fish exposed to these conditions. Pituitary gonadotropin potency, however, is relatively high in fish maintained on short photoperiod-high temperature regimes. 5. 5.|Gonadotrophs were infrequent in the pituitary and pituitary gonadotropin potency was low in animals maintained on short photoperiod-low temperature regimes. These conditions do not promote the final stages of gonadal maturation in Notemigonus . 6. 6.|Light intensities of below 151x are insufficient to induce spawning in Notemigonus . Light intensities above 151x increase the incidence of spawning.

The effects of pinealectomy on pituitary prolactin levels in Carassius auratus exposed to various photoperiod-temperature regimes.

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.

Does pinealectomy, anopsia or exposure to constant darkness affect pituitary prolactin levels in the goldfish,Carassius auratus L.?

SynopsisThe ef fects of exposure to constant darkness, anopsia and pinealectomy on pituitary prolactin levels in the goldfish were examined. Determination of prolactin was made in a polyacrylamide microelectrophoretic system coupled with densitometry. Neither pinealectomy nor anopsia had an effect on pituitary prolactin content in the fall. Exposure to constant darkness in the fall was without obvious effect, whereas such treatment in the spring resulted in significantly elevated pituitary prolactin content. Pinealectomy in the spring did not alter pituitary content, suggesting that the response to constant darkness is independent of the pineal organ, perhaps involving retinal or extra-retinal photoreception.