Differential effects of testosterone plus dihydrotestosterone on male courtship of castrated newts, Taricha granulosa.
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Biomedical subjects
Publications and source records attributed to F L Moore.
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Quaternary amines are unique in their ability to extract metal cyanides from highly alkaline solutions. Cadmium cyanide extracts essentially quantitatively at both the subnanogram and macro levels. Regeneration of the amine solvent is achieved by stripping the cadmium with sodium hydroxide, sodium hypochlorite, or alkaline or acidic formaldehyde solutions. Because they readily extract free cyanide as well as anionic metab cyano complexes, the high-molecular-weight quaternary amines show considerable promise for industrial pollution abatement applications.
Methylmercuric chloride and phenylmercuric acetate extract very efficiently with quaternary amines dissolved in diethylbenzene or other simple solvents. The extraction is effective from either alkaline or acidic solution. The technique considerably extends the scope of conventional solvent extraction practice to permit the extraction and concentration of total mercury in environmental and biological matrices.
Male rough-skinned newts (Taricha granulosa) exhibit an increase in sexual behavior (amplectic clasping) following intracerebroventricular (ICV) injection of adrenocorticotropin (ACTH 1-39), ACTH 4-10, or melanocyte-stimulating hormone (alpha MSH). In contrast, intraperitoneal (IP) administration of ACTH 1-39 or corticosterone significantly decreases the incidence of sexual behavior in male newts. These results suggest that a corticotropin-like peptide acts centrally to enhance sexual behavior and that systemic ACTH acts on the interrenal tissue to inhibit sexual behavior by stimulating the release of corticosterone.
To investigate whether arginine vasotocin (AVT) acts on target cells in the brain of Taricha granulosa (a urodele amphibian), the behavioral effects of intracerebroventricular (ICV) and intraperitoneal (IP) injections of AVT were compared. Male newts exhibited the greatest sexual activity (amplectic clasping) following an ICV injection of 0.1 microgram AVT. Another study showed that nanogram quantities of AVT, administered ICV, stimulated the behavior. An ICV injection of an antagonist to arginine vasopressin, d(CH2)5Tyr(Me)AVP, or an anti-AVT immune serum significantly inhibited the sexual behavior. Intracranial implants of 17 beta-estradiol (E2) or 5 alpha-dihydrotestosterone (DHT) in castrated males maintained the behavioral response to an injection of AVT. Another study found that an IP injection of DHT or E2 did not increase the incidence of newt sexual behavior during the 8 hours following the injection.
Stress-induced corticosterone (CORT) secretion that causes a rapid blockade of courtship clasping by male roughskin newts (Taricha granulosa) is mediated by a specific neuronal membrane receptor for CORT. Amplectic clasping, which can be triggered by pressure on the ventral body surface and cloaca, is controlled by the influence of medullary neurons on the spinal cord. Using clasping as a simple neurobehavioral model, we have focused our analysis of CORT effects on clasping by examining the steroid's effects on neurophysiological properties of medullary neurons, especially medullary reticulospinal neurons, the principal output cells from the brain to the spinal cord. Systemic CORT caused, within 3 min of injection, diverse reductions in reticulospinal neuron excitability. Another rapid CORT effect on medullary neurons was to depress responsiveness to pressure on the cloaca. Experiments with chronically implanted, freely moving newts revealed that the rapid CORT effects are quite specific to neural processes related to clasping. CORT injections rapidly blocked clasping in response to cloacal stimuli and concurrently depressed neuronal responses to cloacal pressure and firing associated with clasping. Activity of reticulospinal neurons was often associated with nonclasping movements and this activity was rarely altered by CORT. Thus, CORT mainly affected aspects of neuronal function related to clasping. In other neurophysiological experiments, we found that the neuropeptides vasotocin and corticotropin-releasing hormone modified the neural effects of CORT. Prior exposure of medullary neurons to either of these neuropeptides caused systemic CORT administration to rapidly potentiate neuronal responses to cloacal stimuli, indicating that the direction and potency of CORT effects depend critically on the prevailing neuroendocrine state of the brain.