PubMed Health⌕ Search

Biomedical subjects

F L Moore

Publications and source records attributed to F L Moore.

At least 37 records · Page 2Linked to original sources
PubMed1997

N-ethylmaleimide (NEM) can significantly improve in situ hybridization results using 35S-labeled oligodeoxynucleotide or complementary RNA probes.

We predicted that a significant source of background labeling after in situ hybridization (ISH) using 35S-labeled probes is attributable to a chemical reaction between the phosphorothioate moiety of the probe [O3P = S] and disulfides in tissue. These covalent bonds would immobilize probe in the tissue, thereby increasing background labeling. On the basis of this view, we have explored the use of N-ethylmaleimide (NEM) to irreversibly alkylate the phosphorothioate moiety of the probe and/or to alkylate free sulfhydryls in tissue to block the formation of disulfides as a method of reducing background labeling. We report that NEM can significantly decrease background labeling of 35S-labeled oligodeoxynucleotide or cRNA probes but does not affect specific labeling. We conclude that the use of NEM in ISH protocols, as outlined here, may be an additional element researchers may consider to improve the signal-to-noise ratio.

Brain Chemistry↗
PubMed1996

Neuroanatomical distribution of androgen and estrogen receptor-immunoreactive cells in the brain of the male roughskin newt.

Immunohistochemistry was used to investigate the neuroanatomical distribution of androgen and estrogen receptors in brains of adult male roughskin newts, Taricha granulosa, collected during the breeding season. Immunoreactive cells were found to be widely distributed in specific brain areas of this urodele amphibian. Androgen receptor-immunoreactive (AR-ir) cells were observed in the olfactory bulbs, habenula, pineal body, preoptic area, hypothalamus, interpeduncular nucleus, area acusticolateralis, cerebellum, and motor nuclei of the medulla oblongata. Estrogen receptor-immunoreactive (ER-ir) cells were found in the lateral septum, amygdala pars lateralis, pallium, preoptic area, hypothalamus, and dorsal mesencephalic tegmentum. This immunocytochemical study of the newt brain reveals AR-ir and ER-ir cells in several regions that have not been previously reported to contain androgen and estrogen receptors in non-mammalian vertebrates. Additionally, the distribution of AR-ir and ER-ir cells in the newt brain, in general, is consistent with previous studies, suggesting that the distribution of sex steroid receptor-containing neurons in some brain regions is relatively conserved among vertebrates.

Animals↗
PubMed1996

Corticotropin-releasing factor enhances locomotion and medullary neuronal firing in an amphibian.

Corticotropin-releasing factor (CRF) administration has been shown to act centrally to enhance locomotion in rats and amphibians. In the present study we used an amphibian, the roughskin newt (Taricha granulosa), to characterize changes in medullary neuronal activity associated with CRF-induced walking and swimming in animals chronically implanted with fine-wire microelectrodes. Neuronal activity was recorded from the raphe and adjacent reticular region of the rostral medulla. Under baseline conditions most of the recorded neurons showed low to moderate amounts of neuronal activity during periods of immobility and pronounced increases in firing that were time-locked with episodes of walking. These neurons sometimes showed further increases in discharge during swimming. Injections of CRF but not saline into the lateral ventricle produced a rapidly appearing increase in walking and pronounced changes (mostly increases) in firing rates of the medullary neurons. CRF produced diverse changes in patterns of firing in different neurons, but for these neurons as a group, the effects of CRF showed a close temporal association with the onset and expression of the peptide's effect on locomotion. In neurons that were active exclusively during movement prior to CRF treatment, the post-CRF increase in firing was evident during episodes of walking; in other neurons that also were spontaneously active during immobility prior to CRF infusion, post-CRF activity changes were evident during immobility as well as during episodes of locomotion. Thus, a principal effect of CRF was to potentiate the level of neuronal firing in a population of medullary neurons with locomotor-related properties. Due to the route of administration CRF may have acted on multiple central nervous system sites to enhance locomotion, but the results are consistent with neurophysiological effects involving medullary locomotion-regulating neurons.

Animals↗
PubMed1996

Catecholamines and indoleamines in the central nervous system of a urodele amphibian: a microdissection study with emphasis on the distribution of epinephrine.

Individual brain nuclei and regions of the central nervous system of adult male roughskin newts (Taricha granulosa) were microdissected, and the concentrations of norepinephrine, epinephrine, 3,4-dihydroxyphenylacetic acid, dopamine, 5-hydroxyindoleacetic acid, and serotonin were determined using high performance liquid chromatography (HPLC) with electrochemical detection. The pattern of distribution of these catecholamines and indoleamines revealed many similarities between this urodele and other vertebrates. The highest concentrations of biogenic amines were observed in brainstem, hypothalamic, and basal forebrain structures; the lowest concentrations were observed in the internal granule layer of the olfactory bulb and pallial structures of the telencephalon. High concentrations of catecholamines and indoleamines were found in hypothalamic periventricular regions that are known to include cerebrospinal fluidcontacting, monoamine-containing neuronal cell bodies. The rostral diencephalon, which included the preoptic recess organ, had high concentrations of the primary catecholamines, norepinephrine and dopamine, and extremely high concentrations of the secondary catecholamine epinephrine. The dorsomedial infundibular hypothalamic region, which included the paraventricular organ, had high concentrations of dopamine and serotonin. The lateral infundibular hypothalamic region, which included the nucleus infundibularis dorsalis, had high concentrations of each of the biogenic amines. The results revealed unique patterns of distribution for each of the catecholamines and indoleamines studied, and provided evidence that regions of the hypothalamus that include cerebrospinal fluid-contacting, monoamine-containing neuronal cell bodies are focal regions for the metabolism of multiple biogenic amines.

Animals↗
PubMed1995

Neurophysiological effects of vasotocin and corticosterone on medullary neurons: implications for hormonal control of amphibian courtship behavior.

Research on a wide variety of vertebrates, from fish to mammals, reveals that corticosteroid hormones and vasotocin-like neuropeptides can potently modulate reproductive behaviors. But, it is not clear how the behavioral effects of these chemical messengers relate to functional properties of behavior-controlling neurons. This problem was investigated in the roughskin newt, Taricha granulosa, an amphibian in which the administration of arginine vasotocin (AVT) facilitates and corticosterone (CORT) inhibits courtship clasping of females by males. In waking, immobilized male newts, neurophysiological effects of AVT and CORT were studied in neurons in the rostral medulla due to the probable role of these neurons in the control of clasping. Topical medullary application of a clasp-facilitating dose of AVT produced a rapid increase in neuronal responsiveness to pressure on the cloaca, a trigger stimulus for clasping responses. Neuronal responses to noncloacal somatic stimuli and to moving visual stimuli were also enhanced. Systemic CORT administration, which has previously been shown to depress newt medullary neuronal sensory responsiveness, reversed the action of AVT such that the peptide depressed sensory responsiveness when applied 30 min after CORT. When AVT application preceded CORT injection by 10-17 min, however, the usual suppressive CORT effect was reversed and this treatment resulted in a rapidly appearing potentiation of neuronal activity and enhanced somatic sensory responsiveness. If the interval between AVT and CORT was increased to 30 min, the steroid caused a rapid depression of firing and a diminished somatic sensory responsiveness in most neurons, similar to what occurs in newts treated with CORT alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Functional studies of corticosterone receptors in neuronal membranes.

This work reviews evidence that some physiological and behavioral responses to steroid hormones use membrane-associated receptors. The review emphasizes research with an amphibian model, Taricha granulosa, but also cites examples from mammalian research. Many studies document steroid responses that occur within a time frame of a few milliseconds or minutes. In Taricha, corticosterone rapidly inhibits reproductive behaviors and causes site-specific changes in neurotransmitter concentrations and neuronal activity. Ligand binding assays using radiolabeled corticosterone and neuronal membranes from Taricha (and other animals) provide evidence that there are high-affinity steroid receptors in neuronal membranes. Subcellular fractionation, autoradiography, and immunocytochemistry add support to the conclusion that there are steroid receptors in neuronal membranes. Other studies indicate that, in Taricha and other animals, there are two types of membrane-associated steroid receptors--ligand-gated ion channels (specifically, the GABAA receptor) and G-protein coupled receptors.

Animals↗
PubMed1994

Gonadotropin-releasing hormones in microdissected brain regions of an amphibian: concentration and anatomical distribution of immunoreactive mammalian GnRH and chicken GnRH II.

Mammalian and chicken II gonadotropin-releasing hormones (mGnRH, cGnRH II) were extracted from 350 microns diameter punches from brains of a urodele amphibian, Taricha granulosa, and measured by means of radioimmunoassay (RIA) with specific antisera. Measurable quantities of both peptides were found in the lateral pallium, the subpallium (along the course of the nervus terminalis), the preoptic area, habenula, optic tectum, infundibulum, paraventricular organ/posterior tubercle of the caudal diencephalon, medulla, and cerebrospinal fluid. Highest concentrations of both peptides were in the preoptic area and infundibulum, suggesting a role in gonadotropin release. In most extrahypothalamic regions, cGnRH II concentrations exceeded those of mGnRH, suggesting that cGnRH II may function as a neurotransmitter in many sites, perhaps to control reproductive behaviors. Results are largely consistent with immunocytochemical (ICC) analyses, except that RIA revealed small amounts of both peptides not found by ICC in some areas of the brain. Results from this microdissection/RIA study and prior ICC studies in amphibians support the conclusions that GnRH cell bodies in the terminal nerve and preoptic area, which project mainly to the median eminence and habenula, express mGnRH, and that GnRH cell bodies in the caudal diencephalon, which project widely throughout the CNS, express cGnRH II. Comparative data support the view that cGnRH II, and the neural systems in which it is expressed, evolved early in vertebrate phylogeny and have been highly conserved.

Animals↗
PubMed1994

Antibodies against different forms of GnRH distinguish different populations of cells and axonal pathways in a urodele amphibian, Taricha granulosa.

Neurons immunoreactive to the peptide hormone gonadotropin-releasing hormone (GnRH) have been identified in the posterior diencephalon or anterior midbrain of diverse vertebrates. These cells are located caudal to the more well-characterized GnRH neurons in the nervus terminalis and septo-preoptic area, and are believed to express one or more of the nonmammalian forms of the GnRH. The present study utilized immunocytochemical techniques to determine whether the posterior GnRH group is present in a urodele amphibian, the newt Taricha granulosa. Antibodies directed against different molecular forms of GnRH were used to evaluate the immunological properties of GnRH-containing neurons in amphibians. An antibody selective for mammalian GnRH labeled perikarya in the nervus terminalis (terminal nerve) and septo-preoptic region, as described previously. Thick fibers that arise from terminal nerve and septo-preoptic neurons project mainly to the median eminence, medial pallium and habenula. An antibody selective for chicken GnRH II labeled cell bodies in the paraventricular organ and posterior tubercle of the caudal diencephalon, and thin fibers that project widely throughout the central nervous system. Region-specific staining with different GnRH antibodies supports the interpretation that different molecular forms of GnRH are expressed by neuroanatomically distinguishable systems.

Animals↗
PubMed1994

Steroid modulation of GABAA receptors in an amphibian brain.

Steroids can modulate gamma-aminobutyric acid (GABAA) receptor function in rat brains, but the physiological relevance of this mechanism is still unclear. To determine whether this phenomenon is widespread among vertebrates, we investigated steroid modulation of GABAA receptors in amphibian brain tissue. Equilibrium binding parameters for t-butylbicyclophosphorothionate ([35S]TBPS) and [3H]flunitrazepam were similar in Taricha granulosa and mammalian brains, as was the allosteric regulation of [35S]TBPS and [3H]flunitrazepam binding by GABA. The rank order and absolute potencies of steroids to inhibit [35S]TBPS binding and enhance [3H]flunitrazepam binding were also similar in Taricha and rat brains. As in mammalian studies, physiological concentrations of corticosterone had no effect on ligand binding or GABA-stimulated Cl- uptake. In autoradiographic studies, 3 alpha-hydroxy-5 alpha-pregnan-20-one inhibited [35S]TBPS binding sites in all brain regions examined, whereas corticosterone had no effect on [35S]TBPS binding. These studies suggest that the steroid recognition sites on GABAA receptors have been highly conserved through vertebrate evolution and thus portend physiologically important functions. However, the pharmacological profiles for the GABAA receptor and the high-affinity corticosteroid receptor are apparently different, suggesting there are multiple types of steroid recognition sites on neuronal membranes.

Animals↗
PubMed1994

Membrane receptors for corticosterone: a mechanism for rapid behavioral responses in an amphibian.

This paper reviews evidence that, in some cases, steroid hormones rapidly modulate behaviors by binding to specific cell-surface receptors on neurons. The evidence comes from research with an amphibian model, Taricha granulosa. In Taricha, stress and corticosterone inhibit reproductive behaviors with a rapidity that is inconsistent with traditional models for steroid action (models in which intracellular steroid receptors function as transcription factors). A series of radioligand binding assay studies identified a corticosteroid receptor in neuronal membranes that appears to mediate the rapid behavioral responses in Taricha. Studies with various steroids showed a strong correlation between their potencies to inhibit the behavior and their potencies to inhibit corticosterone binding. Neurophysiological studies of caudal brainstem neurons found that corticosterone administration rapidly modulates neuronal activity and selectively suppresses sensory processing. Another series of studies provided evidence that this corticosterone receptor interacts with G proteins in neuronal membranes. The studies suggest that there are G protein-coupled receptors for corticosteroids that provide an alternative mechanism by which this hormone regulates brain functions and behaviors.

Animals↗
PubMed1994

Steroid-neuropeptide interactions that control reproductive behaviors in an amphibian.

Investigations into the neuroendocrine regulation of reproductive behaviors in an amphibian (Taricha granulosa) reveal the same basic repertoire of chemical messengers as regulators of male behaviors in other vertebrates. These studies have identified seasonal neural interactions between gonadal steroids and neuropeptides that facilitate male courtship behavior. In addition, this species has served to elucidate how stress-induced suppression of courtship is mediated by corticosterone action through a neuronal membrane receptor and subsequent, rapid neurophysiological effects. These findings indicate that a principal mechanism by which steroids and neuropeptides control male reproductive behavior is the modulation of neural processing of specific sensory stimuli.

Androgens↗
PubMed1993

Rapid neurophysiological effects of corticosterone on medullary neurons: relationship to stress-induced suppression of courtship clasping in an amphibian.

Courtship clasping of females by male roughskin newts (Taricha granulosa) is rapidly blocked by exposure to corticosterone (CORT). This behavioral effect appears to result from CORT binding to a receptor in neuronal membranes. The present study investigated effects of intraperitoneal CORT administration on neurophysiological properties of extracellularly recorded single medullary neurons in acutely prepared newts. CORT produced multiple neurophysiological effects that emerged within 3 min of injection and increased in magnitude during the next 20-30 min. Spontaneously active and sensory-responsive neurons showed a decline or cessation of firing concomitant with a loss of sensory responsiveness, especially to cloacal pressure, a clasp-facilitating stimulus in behaving newts. After CORT administration, reticulospinal neurons that were backfired (antidromically activated) by spinal cord stimulation, exhibited reduced antidromic action potential amplitude, slowed rates of spike generation and other indications of reduced excitability. Comparable effects of CORT were also evident in newts with a premedullary brainstem transection, indicating a direct hormone action on the caudal neuraxis. Dexamethasone (DEX), a glucocorticoid that binds poorly to the CORT membrane receptor and has little effect on clasping, had little or no direct neurophysiological effect, but DEX injection 30 min before CORT interfered with the neurophysiological action of CORT. The rapidity, time course and specificity to CORT of these neurophysiological effects are consistent with mediation through the CORT membrane receptor. In addition, the pattern and dose sensitivity of these neurophysiological actions plus their occurrence in the medulla, suggest that they could underlie the CORT effect on courtship clasping.

Action Potentials↗
PubMed1992

Sexually dimorphic concentrations of arginine vasotocin in sensory regions of the amphibian brain.

Arginine vasotocin (AVT) regulates reproductive behaviors in amphibians. We measured AVT in the brains of bullfrogs (Rana catesbeiana) and newts (Taricha granulosa) using radioimmunoassay. In bullfrogs, AVT concentrations were greater in males, compared to females, in the amygdala pars lateralis, optic tectum, and tegmentum. Concentrations in the dorsolateral nucleus were greater in females. In newts, AVT concentrations were also greater in the tectum and tegmentum of males. AVT may modulate dimorphic behaviors by acting at these sites.

Animals↗
PubMed1992

Evolutionary precedents for behavioral actions of oxytocin and vasopressin.

It is clear that the behavioral actions of oxytocin and vasopressin in mammals are not newly acquired, but have evolutionary antecedents. Injection studies with fish, amphibians, reptiles, and birds indicate that AVT can activate certain reproductive behaviors. The strongest evidence that AVT acts centrally to control reproductive behaviors comes from research on T. granulosa. In this amphibian, injections of AVT agonists activate courtship behaviors (amplectic clasping) in males and egg-laying behaviors in females, whereas injections of AVT antagonists inhibit the behaviors. Also, in Taricha males, AVT concentrations in specific brain areas are associated with the expression of courtship behaviors. Several conclusions about steroid-peptide interactions can be drawn, based on research with this amphibian. First, gonadal steroid hormones act to maintain the behavioral actions of AVT in both males and females. In Taricha, gonadectomy abolishes and steroid implants restore AVT-induced courtship in males and egg-laying in females. Second, gonadal steroids maintain the behavioral actions of AVT, in part, by modulating AVT receptor numbers on target neurons. In Taricha males and females, gonadectomy reduces AVT receptor concentrations (but not binding affinity) in certain brain areas (amygdala pars lateralis) and not others. Third, the type of gonadal steroid determines whether AVT elicits male-like or female-like reproductive behaviors. Ovariectomized Taricha females respond to AVT injections with egg-laying behaviors when implanted with estradiol and with male-like amplectic clasping when implanted with dihydrotestosterone. Fourth, the masculinization of AVT-induced behaviors in females most likely reflects site-specific actions of androgens on AVT-synthesizing neurons. In Taricha, AVTir concentrations in the optic tectum are sexually dimorphic (higher in males than females) and reach peak levels in males during the breeding season. Fifth, AVT content in specific brain areas increase as a function of performing the behaviors. In Taricha, AVTir concentrations in DPOA, CSF, and ventral infundibulum are higher in males that exhibit courtship behaviors than in males that do not. These conclusions illustrate how steroid-peptide interactions in the control of behaviors entail multiple neuroanatomical sites and neurochemical actions.

Animals↗
PubMed1992

Guanyl nucleotides modulate binding to steroid receptors in neuronal membranes.

The recently characterized corticosteroid receptor on amphibian neuronal membranes appears to mediate rapid, stress-induced changes in male reproductive behaviors. Because the transduction mechanisms associated with this receptor are unknown, we performed radioligand binding studies to determine whether this steroid receptor is negatively modulated by guanyl nucleotides. The binding of [3H]corticosterone to neuronal membranes was inhibited by nonhydrolyzable guanyl nucleotides in both equilibrium saturation binding and titration studies. The addition of guanyl nucleotide plus unlabeled corticosterone induced a rapid phase of [3H]corticosterone dissociation from membranes that was not induced by addition of unlabeled ligand alone. Furthermore, the equilibrium binding of [3H]corticosterone and the sensitivity of the receptor to modulation by guanyl nucleotides were both enhanced by Mg2+. These results are consistent with the formation of a ternary complex of steroid, receptor, and guanine nucleotide-binding protein that is subject to regulation by guanyl nucleotides. Therefore, rapid signal transduction through corticosteroid receptors on neuronal membranes appears to be mediated by guanine nucleotide-binding proteins.

Animals↗
PubMed1992

Sex steroids and vasotocin interact in a female amphibian (Taricha granulosa) to elicit female-like egg-laying behavior or male-like courtship.

Female egg-laying behaviors and male amplectic clasping behaviors in the rough-skinned newt (Taricha granulosa) are similar in that animals clasp an object. In the case of egg-laying, females clasp submerged inanimate objects, whereas in amplexus, males clasp conspecific females. Considering these behavioral similarities and differences, we investigated the possibility that gonadal steroids and vasotocin (AVT) interact to control egg-laying behaviors, as has been shown for the control of amplexus in Taricha males. Intact, gravid T. granulosa females injected ip with AVT, unlike those injected with saline, exhibited egg-laying behaviors and oviposition. In ovariectomy-steroid-implant studies, no saline-injected female exhibited egg-laying behaviors, whereas AVT-injected ovariectomized females exhibited egg-laying behaviors if implanted with estradiol (E2), testosterone, or dihydrotestosterone (DHT), and not if implanted with empty capsules. When given a choice between clasping aquatic vegetation or other females (amplectic clasping), following an AVT injection, unoperated and sham-operated control females and ovariectomized females with E2 implants did not preferentially clasp aquatic vegetation over other females. In contrast, AVT-injected ovariectomized females with DHT implants preferentially clasped other females. Thus, exposure of Taricha females to estrogens or androgens appears to determine whether the AVT-induced clasping is egg-laying or amplectic clasping.

Animals↗
PubMed1991

A corticosteroid receptor in neuronal membranes.

Steroids may rapidly alter neuronal function and behavior through poorly characterized, direct actions on neuronal membranes. The membrane-bound receptors mediating these behavioral responses have not been identified. [3H]Corticosterone labels a population of specific, high-affinity recognition sites (dissociation constant = 0.51 nanomolar) in synaptic membranes from an amphibian brain. These binding sites were localized by receptor autoradiography in the neuropil, outside the regions of perikarya. The affinities of corticoids for this [3H]corticosterone binding site were linearly related to their potencies in rapidly suppressing male reproductive behavior. Thus, it appears that brain membranes contain a corticosteroid receptor that could participate in the regulation of behavior.

Amphibians↗