Monoaminergic changes associated with socially induced sex reversal in the saddleback wrasse.

The process of sex reversal in fishes is socially mediated and requires a total reorganization of the hypothalamo-pituitary-gonadal axis. When the ratio of males to females in a population of saddleback wrasse (Thalassoma dupperrey) is too low, the largest female becomes male over the course of 6 to 8 weeks. This event requires the conversion of external social cues into internal chemical cues. In an attempt to investigate the role monoamines might play in this process, two females were housed together in floating enclosures in order to induce sex reversal in the larger. Brains were sampled at various time points throughout the process of sex reversal. Monoamines were measured in the amygdala, preoptic area, ventral hypothalamus, locus coeruleus and raphe nucleus. Changes were demonstrated in monoamine metabolism for all brain regions examined. The most important changes in monoamine-system activation were seen during the first week of sex reversal. It is during this time that transitional animals undergo behavioral sex reversal. There is an increase in serotonergic activity in the amygdala which is likely related to territorial acquisition. The absence of male aggression results in a less stressful environment for the female and a reduction in serotonergic activity in the preoptic area allowing for an increase in noradrenergic activity potentially triggering the reorganization of the reproductive axis. In the ventral hypothalamus, there is a decrease in noradrenergic and increase in dopaminergic activity associated with this change from female to male. The locus coeruleus shows an increase in noradrenergic activity later in the process of sex reversal which is probably a response to more circulating androgens. In the raphe nucleus, there is a decrease in serotonergic activity at the time of behavioral sex reversal. This decrease in serotonergic activity is linked to the behavioral component of sex reversal. This study suggests that monoamines play a very important role in both behavioral and gonadal sex reversal in the saddleback wrasse, the former under the control of serotonin in the raphe and the latter mediated via serotonergic effects on norepinephrine in the preoptic area.

Some aspects of hepatic function in feral brown trout, Salmo trutta, living in metal contaminated water.

Brown trout, Salmo trutta, exposed to heavy metals (mainly Cd and Zn) for at least 2 years in the Eagle River, Colorado, were examined for liver size and activity of the growth-promoting enzyme, ornithine decarboxylase (ODC) and compared to trout living in an uncontaminated site. Liver-somatic index (LSI) was greater for trout living in the uncontaminated site with the LSI of females being significantly greater than that of males. The LSI for females at the uncontaminated site was greater than that of females at the contaminated site, but males were not different statistically. ODC activity in the livers of both males and females was lower at the contaminated site. However, males and females did not differ with respect to ODC activity. These data suggest that chronic exposure to heavy metals may have important implications for growth and reproduction and possibly survival. The activity of ODC in liver might serve as a useful biomarker when assessing chronic toxicity of metals to naturally reproducing fish populations.

Elevation of plasma cortisol during the spawning migration of landlocked kokanee salmon (Oncorhynchus nerka kennerlyi).

Kokanee salmon (Oncorhynchus nerka kennerlyi ), a landlocked subspecies of sockeye salmon, exhibited hypothalamic-pituitary interrenal (HPI, adrenal homologue) axis activation and an increase in plasma cortisol concentration up to 639 +/- 55.9 ng/ml in association with upstream migration in the upper Colorado River even though they were not exposed to a change in salinity and lengthy migration. Kokanee salmon were collected at various stages of migration and concomitant sexual maturation. The pattern of cortisol elevation in kokanee is similar to that in ocean-run sockeye salmon (O. nerka nerka). The presence of plasma cortisol elevation in an upstream migrating, landlocked Pacific salmon suggests that stressors previously considered to cause the cortisol increase, such as long-distance migration and changes in salinity, may not be primary causes of the HPI axis activation.

Distribution of beta-amyloid and amyloid precursor protein in the brain of spawning (senescent) salmon: a natural, brain-aging model.

Brain amyloid precursor protein (APP), a normal constituent of neurons, glial cells and cerebrospinal fluid, has several proposed functions (e.g., in neuronal growth and survival). It appears, however, that altered processing of APP is an initial or downstream step in the neuropathology of brain aging, Alzheimer's disease (AD), and Down's syndrome (DS). Some studies suggest that proteolytic cleavage of APP, producing beta-amyloid (Abeta(1-42)), could have neurotoxic or neuroprotective effects. In this study, we utilized antibodies to human APP(695) and Abeta(1-42,) and Congo red staining, to search for amyloid deposition in the brain of semelparous spawning kokanee salmon (Oncorhynchus nerka kennerlyi). Intracellular APP(695) immunoreactivity (APP-ir) was observed in brain regions involved in gustation (glomerulosus complex), olfaction (putative hippocampus, olfactory bulb), vision (optic tectum), the stress response (nucleus preopticus and nucleus lateralis tuberis), reproductive behavior (nucleus preopticus magnocellularis, nucleus preopticus periventricularis, ventral telencephalon), and coordination (cerebellum). Intra- and extra-neuronal Abeta(1-42) immunoreactivity (Abeta-ir) were present in all APP-ir regions except the nucleus lateralis tuberis and Purkinje cells of the cerebellum (coordination). Thus, the relationship between APP and Abeta deposition during brain aging could shed light on the processing of APP into Abeta, neurodegeneration, and possible protection of neurons that are functioning in spawning but senescent salmon. Pacific salmon, with their predictable and synchronized life history, could provide research options not available with the existing models for studies of brain aging and amyloidosis.

Cell density and intracellular translocation of glucocorticoid receptor-immunoreactive neurons in the kokanee salmon (Oncorhynchus nerka kennerlyi) brain, with an emphasis on the olfactory system.

This study tested the hypothesis that neurons in olfactory regions of the kokanee salmon brain contain glucocorticoid receptors. Distribution and neuronal number of glucocorticoid receptor-like immunoreactive (GRir) neurons were identified in the kokanee salmon brain using immunohistochemistry with an antibody to GR (polyclonal rabbit anti-human, dilution 1:1500; and monoclonal mouse, dilution 5 micrograms/ml). Distribution of GRir neurons similar to the mammalian pattern was observed in the brains of sexually immature (n = 8; 4 female and 4 male) as well as spawning (n = 8; 4 female and 4 male) salmon. Olfactory-related areas containing GRir positive neuronal bodies included the internal cell layer of the olfactory bulb, ventral-lateral and lateral parts of the dorsal telencephalon (homologue of the mammalian hippocampus), ventral area of the telencephalon (homologue of the mammalian amygdala), glomerulosus complex of the thalamus, the preoptic area, and inferior lobe of the hypothalamus. The pattern of GRir neuronal distribution in sexually immature and spawning fish was similar. However, spawning fish brains, compared to sexually immature brains, exhibited a significantly greater GRir neuronal number in several olfactory regions in paired immunohistochemical runs. There also were differences in intraneuronal location of GRir in olfactory regions, with staining being predominantly cytoplasmic in sexually immature fish but nuclear in spawning fish. These results are consistent with a role for cortisol in olfactory-mediated homing in kokanee salmon. Although GRir were identified in many nonolfactory regions, the focus of this study is on GRir present in brain regions involved in olfaction.

Use of fecal material to associate a suspect with a crime scene: report of two cases.

Fecal matter analyses were applied to two cases: a homicide and a robbery. Scrapings of fecal matter removed from samples of clothing obtained from a homicide suspect were examined for their plant cell and cell fragment content and compared with fecal matter from a rape-homicide victim and scrapings from her clothing. Scrapings were hydrated and examined microscopically. Types of food plants were identified from the observed cells by comparison with known food plants. A similar analysis was conducted on the clothing of a robbery suspect and compared with fecal material left at the crime scene. The results showed that, respectively in the two cases, the reference samples were remarkably similar, if not identical, to those from the suspects' clothing.

Impaired adrenocortical response to stress by brown trout, Salmo trutta, living in metal-contaminated waters of the Eagle River, Colorado.

Brown trout, Salmo trutta, were collected from two sites contaminated with cadmium (Cd) and zinc (Zn) and one uncontaminated site. These fish were subjected to a continuous confinement stressor in wire cages placed in the river (moderate stress) or in 5-gal. plastic buckets on land (severe stress). Plasma cortisol and corticotropin (ACTH) were determined for fish in buckets by radioimmunoassay after 0, 1, 3, 12, or 24 h of confinement. Plasma cortisol and ACTH levels of brown trout from both contaminated and uncontaminated sites initially were the same and increased with time. However, the rise in plasma cortisol was delayed significantly in fish residing in contaminated sites, even though ACTH secretion initially was elevated compared with control trout. Furthermore, secretion of cortisol and ACTH by these fish declined significantly between 3 and 24 h of confinement. Fish from the uncontaminated site responded more rapidly to confinement with increased cortisol secretion and elevated levels of ACTH and continued to exhibit elevated levels of both hormones up to 24 h of confinement. Caged fish examined after 0, 3, 12, and 24 h of confinement exhibited similar plasma cortisol responses regardless of previous exposure to metals. These results suggest that the overall response to severe, short-term confinement stress by the hypothalamo-pituitary-adrenocortical axis of fish chronically exposed to Cd and Zn was depressed and that these fish could not sustain the stress response as readily as fish living in uncontaminated water.

Interactions of gonadal steroids and pesticides (DDT, DDE) on gonaduct growth in larval tiger salamanders, Ambystoma tigrinum.

In view of the current worldwide decline in amphibian populations, exploratory studies are needed to assess the potential for environmental contaminants to act as endocrine disrupters of the amphibian reproductive system. The present study investigated the effects of DDT dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) on the development of amphibian gonaducts. Larval male and female tiger salamanders (Ambystoma tigrinum), with immature gonads, were immersed in a sublethal solution of p,p'-DDE or technical-grade DDT (80% p,p'-DDT and 20% o,p'-DDT). Additionally, larvae were injected with the steroid hormones estradiol or dihydrotestosterone (DHT). Morphometrics were used to analyze the effects and interactions of steroid and pesticide treatments on larval gonaducts. Estradiol and DHT stimulated cell proliferation and hypertrophy of the müllerian duct epithelium in both sexes. Wolffian duct epithelium, however, was stimulated only by DHT treatment. The pesticide DDT antagonized the estrogenic actions of the steroid treatments, and p,p'-DDE acted as an estrogen on the müllerian ducts of females only. The müllerian ducts of males, and the wolffian ducts of both sexes, were unaffected by DDT or DDE alone. While confirming the previously reported estrogenic actions of estradiol and DHT on urodelean gonaducts, the results contradict the expected estrogenic actions of DDT and antiandrogenic actions of p,p'-DDE. Instead, in A. tigrinum, technical-grade DDT had an antiestrogenic action and p,p'-DDE an estrogenic action.

Interactions of androgens and estradiol on sex accessory ducts of larval tiger salamanders, Ambystoma tigrinum.

Immature tiger salamander larvae were treated with 12.5 or 25 micrograms of estradiol, testosterone, or dihydrotestosterone (DHT), or 12.5 micrograms of estradiol combined with 12.5 micrograms of either testosterone or DHT. Müllerian duct epithelium was more stimulated by combined steroid treatment than by any steroid alone. Estradiol antagonized the action of DHT in the Wolffian duct. Both of the androgens and estradiol when administered alone at the higher dose stimulated enlargement of connective tissue surrounding the ducts, but the combined 12.5 micrograms androgen/12.5 micrograms estrogen treatment was more effective even though the total steroid administered was the same. The effectiveness of DHT on müllerian cells of this species is evidence against a required aromatization of androgens to explain paradoxical steroid effects and suggests that fundamental differences may exist in steroid receptors of müllerian ducts, connective tissue, and Wolffian ducts. A possible role for the urodele duct system for assessing estrogenic activity of environmental contaminants is discussed.

Immunocytochemical and histological differences in the interrenal axis of feral brown trout, Salmo trutta, in metal-contaminated waters.

There are more CRH-like immunoreactive neurons in the preoptic nucleus and nucleus lateralis tuberis in the brain of feral brown trout, Salmo trutta, living in cadmium- and zinc-contaminated regions of the Eagle River than in fish from an uncontaminated control site. Histological analyses revealed that interrenal cells are more stimulated (exhibiting both hypertrophy and hyperplasia) in fish living in contaminated sites than interrenal cells of fish at the control site. These results suggest that the hypothalamo-pituitary-interrenal (HPI) axis of fish living in the metal-contaminated water shows evidence of chronic stimulation. We suggest that assessment of these parameters of the HPI axis may be useful indices of chronic environmental stress in trout.

A glycinergic intervention potentiates the antiseizure efficacies of MK-801, flurazepam, and carbamazepine.

Twenty four hours after mice were forced to swim for up to 10 minutes in cold water, there was a reduction in the ability of MK-801 to antagonize the electrical precipitation of tonic hindlimb extension. Milacemide, a lipophilic prodrug of glycine, restored the antiseizure efficacy of MK-801 to the same level observed in unstressed animals treated with milacemide and MK-801. Stimulation of the glycine-gated chloride ionophore subsequent to the liberation of free glycine could explain milacemide's pharmacologic action as an adjuvant to MK-801. Consistent with this interpretation, milacemide was able to potentiate the antiseizure effects of flurazepam, a benzodiazepine agonist, in stressed and unstressed mice and carbamazepine in unstressed animals. D-cycloserine, a partial glycine agonist with greater specificity for the strychnine-insensitive modulatory site on the NMDA receptor complex, was examined for its effect on MK-801's antiseizure efficacy. At a high dose (320 mg/kg), D-cycloserine alone had an anticonvulsant effect. Moreover, this dose of D-cycloserine administered with MK-801 showed a significantly greater anticonvulsant efficacy than MK-801 alone. The data support the development of glycinergic interventions as adjunctive agents in the pharmacotherapy of seizure disorders.

Glycinergic interventions potentiate the ability of MK 801 to raise the threshold voltage for tonic hindlimb extension in mice.

Milacemide, an acylated prodrug of glycine, was able to increase the efficacy with which [+]-5-methyl-10,11-dihydro-5h-dibenzo[a,d]cyclohepten-5,10-imine meleate (MK 801) antagonized the electrical precipitation of seizures in mice. The mechanism of milacemide's potentiation of MK 801's antiseizure efficacy in intact mice is unclear; however, a glycine agonist selective for the strychnine-insensitive site on the NMDA receptor complex was also able to potentiate MK 801. The exciting possibility exists that an exogenous glycinergic intervention can potentiate NMDA-mediated neural transmission in intact animals.

Monoamines and their metabolites in the amphibian (Ambystoma tigrinum) brain: quantitative changes during metamorphosis and captivity.

1. Monoamine neurotransmitters (epinephrine, norepinephrine, dopamine, serotonin and some of their metabolites (DOPEG, MHPG, DOPAC, 5-HIAA) were measured by HPLC in extracts from telencephalon (TEL) and diencephalon-midbrain (DM) before, during at the end of metamorphosis. 2. During metamorphosis MHPG increased and 5-HIAA decreased in TEL and DM while DOPEG decreased only in DM. 3. Monoamine levels were greater in the TEL and a larger increase in MHPG occurred there. 4. Captivity without metamorphosis also caused a significant depression of 5-HIAA in TEL and depression of DOPEG, MHPG and DOPAC in DM.

Reduction of flurazepam's antiseizure efficacy persists after stress.

Twenty-four hours after mice were forced to swim for up to 10 min in cold (6 degrees C) water, the ability of flurazepam to antagonize the electrical precipitation of seizures was reduced. This stress-induced reduction in flurazepam's antiseizure efficacy persisted for at least 72 h; but was absent 1 week after the single session of swim stress. The data may be relevant to stress-related psychiatric disorders and suggest that the therapeutic efficacy of benzodiazepines may be altered after a severe stress.

Paradoxical effect of flurazepam.

Cold water swim stress has been shown to decrease the ability of flurazepam, a prototypic GABA-positive benzodiazepine, to antagonize the electrical precipitation of seizures in mice. This stress-induced reduction in the antiseizure efficacy of flurazepam is not due to a reduction in the threshold voltage for seizure production. In this study, we examined the effect of treating mice with flurazepam 20 min prior to cold water swim stress on its ability to antagonize electrically precipitated seizures 24 h later. Contrary to our expectation, pretreatment with flurazepam potentiated the stress-induced reduction of its antiseizure efficacy.

Effects of milacemide, a glycine prodrug, on ethanol's antiseizure efficacy.

A variety of in vitro data suggest that ethanol interferes with N-methyl-D-aspartate (NMDA)-stimulated calcium ion conductance. This effect occurs at ethanol concentrations in blood associated with acute intoxication in the nontolerant human (less than 50 mM) and may involve its selective action at the strychnine-insensitive glycine binding site on the NMDA receptor complex. Moreover, there are in vitro data showing that glycinergic interventions can attenuate ethanol's inhibitory actions on NMDA-mediated transmission. The relevance of these in vitro findings to the intact animal was tested in an incremental electroconvulsive shock (IECS) paradigm using milacemide, a lipophilic prodrug of glycine. In this paradigm, the influence of milacemide on ethanol's ability to antagonize the electrical precipitation of seizures was tested. Doses of 3.2 and 32.0 mg/kg did not change ethanol's antiseizure efficacy, whereas 320.0 mg/kg potentiated ethanol's antiseizure efficacy. The mechanism of potentiation of ethanol's antiseizure efficacy by milacemide is unknown. Potentiation could result from stimulation of chloride ion conductance in the brainstem by glycine liberated from the lipophilic prodrug and acting at the strychnine-sensitive site. Alternatively, unmetabolized milacemide, which accumulates at the highest administered dose, may antagonize NMDA-mediated neural transmission. The latter explanation would be consistent with a role for receptor-gated calcium ion conductance in the mediation of ethanol's actions.

The effects of orchidectomy and gonadotropins on steroidogenesis and oogenesis in Bidder's organs of the toad Bufo woodhousii.

In the family Bufonidae, male toads possess rudimentary ovaries, called Bidder's organs, which are attached to the testes. The mechanisms involved in the inhibition of oogenesis in these structures were investigated in male Bufo woodhousii. Orchidectomized and sham-operated animals were injected with gonadotropins (pregnant mare serum gonadotropin [PMSG] + human chorionic gonadotropin [hCG]) for 26 days and the effects of these hormones on oogenesis and steroidogenic activity (3 beta-hydroxysteroid dehydrogenase [3 beta-HSD] and 17 beta-HSD) in the Bidder's organ were quantified. Bilateral orchidectomy alone resulted in the growth of bidderian oocytes and a shift towards later stages of oogenesis. Gonadotropins enhanced this effect and stimulated the proliferation of new germ cells. In the presence of testes, however, bidderian oogenesis remained inhibited despite high levels of circulating gonadotropins. In both ooplasm and follicular layers of the bidderian oocytes of all toads, 3 beta-HSD and 17 beta-HSD activities were detected by histochemistry. Follicular enzymatic activity increased in orchidectomized toads treated with PMSG + hCG but decreased in sham-operated toads treated with gonadotropins. Testis weights, rudimentary oviduct weights, and plasma steroid levels increased in intact toads injected with hCG + PMSG. Gonadotropins had no effect on plasma steroid levels in orchidectomized toads, however. These results suggest that the testes play a major role in the inhibition of oogenesis in Bidder's organs of B. woodhousii and are a major source of androgens. High circulating levels of gonadotropins do not overcome the inhibitory effects of the testes.

Organization of tyrosine hydroxylase-immunoreactive neurons in the di- and mesencephalon of the American bullfrog (Rana catesbeiana) during metamorphosis.

We examined the immunocytochemical distribution of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis, in the di- and mesencephalon of developing bullfrog tadpoles. Special attention was given to catecholaminergic innervation of the median eminence and pituitary. In premetamorphic tadpoles, tyrosine hydroxylase-immunoreactive neurons were visualized in the suprachiasmatic and infundibular hypothalamus, the ventral thalamus, and midbrain tegmentum by Taylor-Kollros stage V. The number of labeled neurons in all these areas increased as metamorphosis progressed. By mid-prometamorphosis, labeled neurons appeared in the preoptic recess organ as well as in the posterior thalamic nucleus. The majority of cells in the preoptic recess organ, as well as occasional neurons in the suprachiasmatic nucleus, exhibited labeled processes which projected through the ependymal lining of the preoptic recess to contact cerebrospinal fluid. The modified CSF-contacting neurons of the nucleus of the periventricular organ were devoid of specific staining. By late prometamorphosis, labeled fibers from the suprachiasmatic nucleus were observed projecting caudally to enter the hypothalamo-hypophysial-tract en route to innervating the median eminence and pituitary. Labeled fibers arising from the dorsal infundibular nucleus projected ventrolaterally to contribute to catecholaminergic innervation of the median eminence and pituitary. Immunoperoxidase staining of tyrosine hydroxylase-immunoreactive fibers and terminal arborizations in the median eminence were restricted to non-ependymal layers, while labeled fibers in the pituitary were observed in the pars intermedia and pars nervosa. Staining of tyrosine hydroxylase-immunoreactive fibers in the median eminence and pituitary was sparse or absent in premetamorphic tadpoles, but became increasingly more intense as metamorphosis progressed.

Immunohistochemical localization of corticotropin-releasing factor- and arginine vasotocin-like immunoreactivities in the brain and pituitary of the American bullfrog (Rana catesbeiana) during development and metamorphosis.

Immunoperoxidase staining for corticotropin-releasing factor (CRF) in the median eminence was sparce or absent from premetamorphic tadpoles, but increased dramatically by late prometamorphosis. Quantitative photometry revealed that CRF-like immunostaining material in the median eminence was most dense in metamorphic climax tadpoles. Arginine vasotocin (AVT)-like immunostaining material was visualized in perikarya of the magnocellular nucleus, with extensive fiber staining seen in the medial basal and infundibular hypothalamus as well as in the median eminence and pars nervosa of the pituitary. AVT-like immunoreactive perikarya were virtually absent in premetamorphic tadpoles, but their number increased greatly by Taylor-Kollros stage XII and continued to increase after this stage. Quantitative photometry revealed that AVT-like immunoreactivity in the pars nervosa increased greatly at Taylor-Kollros stage XII and remained intense after this stage. AVT-like immunoreactivity did not appear in the median eminence until Taylor-Kollros stage XVI. Localization of AVT-like immunoperoxidase staining around portal vessels in the median eminence suggests an anatomical mechanism for delivery of AVT to anterior pituitary corticotropes. These results indicate that both CRF and vasotocinergic neuronal systems develop just before the activation of interrenal steroidogenesis which occurs during the later stages of metamorphosis in this species.

Induction of cloacal and dermal skin glands of tiger salamander larvae, (Ambystoma tigrinum): effects of testosterone and prolactin.

Treatment of male and female tiger salamander larvae with testosterone (0.3 micrograms/g body weight/day) induced precocious formation of ventral cloacal glands and stimulated proliferation and differentiation of mucous and granular (serous) glands in the ventral dermis of the skin. Lower doses of testosterone produced no visible glandular effects but did cause hyperemia and edema in the cloacal region. Prolactin (0.5 micrograms/g body weight/day) enhanced the action of testosterone on the cloacal glands, increasing both the amount of gland induced and the degree of glandular secretion. There was no apparent effect of prolactin alone on cloacal glands or any effect of prolactin with or without testosterone on the dermal glands. The possible homology of the amphibian ventral cloacal gland to the mammalian prostate gland is discussed.