Immune function, hepatic CYP1A, and reproductive biomarker responses in the gulf killifish, Fundulus grandis, during dietary exposures to endocrine disrupters

The gulf killifish, Fundulus grandis, was used to determine the influence of biological rhythms on three biomarker responses. We first developed monoclonal antibodies against the model's immunoglobulins and vitellogenin in order to measure antibody responses and vitellogenesis, respectively. We then treated adults with 10, 1, 1, and 10 ppm of Aroclor 1254, tribuyltin, 3-methylcholanthrene, and nonyl-phenol, respectively, in mixtures over a 16-week period. The study followed Vibrio anguillarum-specific antibody responses, hepatic CYP1A, and plasma vitellogenin levels in the morning and again in the evening at 2-week intervals. The contaminated diet suppressed secondary antibody responses, but only in the morning. The contaminated diet also altered CYP1A, but not vitellogenesis. In addition, fish in the control group exhibited daily and seasonal differences in specific antibody levels and CYP1A induction. Moreover, circulating vitellogenin levels in control males sampled in the morning increased throughout the exposure, but remained below those of females. This study underscores the need to consider normal physiological rhythms when employing biomarkers in toxicology.

Timed daily administrations of hormones and antagonists of neuroendocrine receptors alter day-night rhythms of allograft rejection in the gulf killifish, Fundulus grandis

Immune activity during scale allograft rejection, measured by melanophore destruction, is two to three times greater at night (12-hr scotophases) than during the day (12-hr photophases) in gulf killifish (Fundulus grandis). In the present study of killifish, hormones and antagonists of neuroendocrine receptors were administered daily at 0800 or 2000 hr during either 12-hr photoperiods (light onset: 0800 hr) or continuous light to examine possible neuroendocrine regulation of the allograft rejection rhythm. Immune activity peaked 0-12 hr after the time of daily growth hormone injections (0800 or 2000 hr) in fish held under continuous light and examined twice daily (0800 and 2000 hr) for melanophore breakdown. Immune activity peaked 12-24 hr after the time of day when cortisol-supplemented meals were provided (light onset or light offset) whether fish were treated throughout the days of melanophore examinations or pretreated for 3 days only prior to melanophore examinations. Daily rhythms of immune activity were not observed in fish treated with propranolol or naloxone at light offset only, growth hormone or atropine at light onset only, or prolactin at either light onset or light offset; these timed-treatments also reduced (prolactin or growth hormone) or prolonged (propranolol or naloxone) the length of time needed to destroy all melanophores within an allograft compared with controls. These results demonstrate that neuroendocrine factors can modulate a daily rhythm of immune function in fish.

Nonphotic stimuli alter a day-night rhythm of allograft rejection in gulf killifish

The influence of environmental stimuli on a daily rhythm of immune activity during scale allograft rejection was investigated in gulf killifish, Fundulus grandis. Although melanophore destruction in the grafts is largely restricted to the scotophases in killifish held on 12 h daily photoperiods (LD 12:12), timed daily netting (tank-transfer "stress"), thermoperiods (from 20 degrees to 30 degrees C for 4 or 12 h), and feeding altered the expression of this rhythm. Melanophore breakdown peaked 0-12 h after netting or thermoperiod onset and 12-24 h after feeding, whether the fish were exposed to these nonphotic daily stimuli at the onset or offset of 12-h photoperiods. In fish held under continuous light and pretreated with these daily stimuli, 24-h immune activity rhythms persisted in the altered phases for several days after the daily treatments were stopped. These findings suggest that a daily rhythm of immune activity may have adaptive significance in fish.

A day-night rhythm of immune activity during scale allograft rejection in the gulf killifish, Fundulus grandis

The circadian variation of scale allograft rejection was studied in teleost fish maintained on 12-h daily photoperiods (LD 12:12). Immune activity, measured by melanophore breakdown, was two to three times greater during the dark than during the light whether scale allografts were transplanted at light onset or light offset. Because rejection occurred predominantly at night, survival times of both primary and secondary allografts were about 0.4 days longer when the transplants were made at light onset. Immune activity undergoes a robust daily variation in a teleost fish.

Evidence of aberration of the natural cytotoxic cell activity in Fundulus heteroclitus (Pisces: Cyprinodontidae) from the Elizabeth River, Virginia

There is a general agreement that exposure to high concentrations of polynuclear aromatic hydrocarbons (PAH) in sediments is associated with high frequencies of neoplasms in feral fish species. Since PAH modulate the activity of murine and amphibian natural cytotoxic (killer) cells, a leukocyte subpopulation that is believed to play an important role in immunosurveillance, we wished to determine if fish exposed to PAH could have an altered natural cytotoxic cell (NCC) activity. In the present study, mummichog (Fundulus heteroclitus L.) were collected from two sites in the Elizabeth River, VA that are heavily contaminated with PAH, and from a relatively unpolluted reference site in the York River, VA. The cytotoxic activity of anterior kidney and splenic leukocytes was tested against the tumor cell line K562. The leukocytes from Elizabeth River fish displayed a significant depression of the in vitro tumorilytic activity as compared with leukocytes from the York River fish. Analysis of leukocyte-tumor cell conjugates indicated that Elizabeth River fish leukocytes were unable to recognize and subsequently bind to the tumor target cells. This suggests an aberration in the early events of the cytotoxic mechanism. By keeping the fish in cleaner York River water for up to 28 weeks the suppressed NCC activity was reversed totally in one site, which is slightly contaminated, and partially in the other site, which is heavily polluted with creosote from an operating wood treatment plant. This indicates that the decreased NCC activity was related, at least in part, to exposure to the chemical pollutants in the Elizabeth River sediments.

Serological alterations in carcinogen-exposed teleosts: procedures for preparation and analysis of samples from small fish

To study the effects of environmental carcinogens on the immune system of Cyprinodon variegatus, we had to miniaturize or modify standard immunological procedures due to the small size of the fish. Modifications in standard bleeding procedures allowed collection of sufficient serum for most serological procedures. Serum electrophoresis showed considerable variation between exposed and unexposed fish as did qualitative immunoelectrophoresis techniques. We successfully adapted a bacteriophage neutralization procedure for use with the C. variegatus system to measure antiviral antibodies. The presence of antibody-forming cells in spleen suspensions from fish immunized with human type O erythrocytes was demonstrated by a modified immune rosette procedure. A capillary tube procedure was developed for separation of leukocytes from erythrocytes in blood from C. variegatus.