Second messenger systems underlying amine and peptide actions on cardiac muscle in the horseshoe crab, Limulus polyphemus

The biochemical mechanisms by which octopamine, catecholamines and the peptide proctolin exert their actions on Limulus cardiac muscle were investigated. Amines produced long-lasting increases in the amplitude of contractions evoked by electrical stimulation. At 10(−5) mol l-1, the apparent order of potency for amine-induced increases in evoked contraction amplitude was dopamine approximately equal to octopamine greater than norepinephrine approximately equal to epinephrine. At this dose, amines produced long-lasting increases in the levels of cyclic AMP (octopamine greater than dopamine approximately equal to norepinephrine approximately equal to epinephrine), but not of cyclic GMP, in Limulus cardiac muscle. Like the amines, the adenylate cyclase activator forskolin enhanced cardiac muscle contractility and increased levels of cyclic AMP, but not of cyclic GMP. The phosphodiesterase inhibitor IBMX produced a transient increase in cardiac muscle contractility, but typically produced long-lasting negative inotropy. This agent increased levels of both cyclic AMP and cyclic GMP in Limulus cardiac muscle. Proctolin and the protein kinase C activator phorbol dB increased the contraction amplitude of the intact heart and the electrically stimulated myocardium. These compounds, as well as dopamine, elicited sustained contractures and rhythmic contractions when applied to deganglionated Limulus cardiac muscle rings. Unlike the amines, proctolin and phorbol dB did not increase cardiac muscle cyclic AMP levels. These results suggest that several second-messenger systems may be utilized by amines and peptides to produce excitatory actions on cardiac muscle fibers of the Limulus heart. Cyclic AMP appears to be an important second messenger underlying the effects of amines to enhance cardiac muscle contractility. Pharmacological data suggest that proctolin may alter cardiac muscle contractility and excitability by a mechanism which involves the phosphatidylinositol pathway. Dopamine, unlike the other amines, produces a number of proctolin-like effects and may activate both the cyclic AMP and the phosphatidylinositol systems in Limulus cardiac muscle

Involvement of cyclic AMP in multiple, excitatory actions of biogenic amines on the cardiac ganglion of the horseshoe crab Limulus polyphemus

Cyclic AMP appears to be involved in several excitatory actions of amines on neurones of the Limulus cardiac ganglion. Amines selectively increase levels of cardiac ganglion cyclic AMP with a magnitude and time course similar to that observed for amine-induced excitation of cardiac ganglion burst rate. With respect to either the physiological or biochemical effect, the apparent order of potency is octoparnine\u3eepinephrine==dopamine\u3enorepinephrine. Elevation of cardiac ganglion cyclic AMP levels by octopamine or dopamine is dose-dependent and is potentiated by the phosphodiesterase inhibitor 3-isobutyl 1-methylxanthine (IBMX). Several pharmacological agents which influence cyclic nucleotide metabolism, including forskolin, IBMX and 8-substituted cyclic AMP analogues, have amine-like effects on the Limulus cardiac ganglion. These effects include increased burst rate of the isolated cardiac ganglion and decreased burst duration, interburst interval and number of spikes per burst in follower neurones. Forskolin and IBMX increase levels of cardiac ganglion cyclic AMP, and IBMX also increases cyclic GMP levels in this tissue. Amines, forskolin and IBMX have direct effects on follower neurones pharmacologically isolated from pacemaker cell input. Octopamine, forskolin and IBMX depolarize follower neurones, while dopamine hyperpolarizes these cells. Amines, forskolin and IBMX elicit burst-like potentials in follower neurones, and increase the size of evoked, unitary junction potentials recorded in cardiac muscle fibres. These pharmacological and biochemical data suggest that multiple, excitatory effects of biogenic amines on the Limulus cardiac ganglion are mediated by simultaneous increases in cyclic AMP at several loci within this neural network

Intracellular immunohistochemical detection of tetrodotoxin in Pleurobranchaea maculata (Gastropoda) and Stylochoplana sp. (Turbellaria)

Tetrodotoxin (TTX), is a potent neurotoxin targeting sodium channels that has been identified in multiple marine and terrestrial organisms. It was recently detected in the Opisthobranch Pleurobranchaea maculata and a Platyhelminthes Stylochoplana sp. from New Zealand. Knowledge on the distribution of TTX within these organisms is important to assist in elucidating the origin and ecological role of this toxin. Intracellular micro-distribution of TTX was investigated using a monoclonal antibody-based immunoenzymatic technique. Tetrodotoxin was strongly localized in neutral mucin cells and the basement membrane of the mantle, the oocytes and follicles of the gonad tissue, and in the digestive tissue of P. maculata. The ova and pharynx were the only two structures to contain TTX in Stylochoplana sp. Using liquid chromatography-mass spectrometry, TTX was identified in the larvae and eggs, but not the gelatinous egg cases of P. maculata. Tetrodotoxin was present in egg masses of Stylochoplana sp. These data suggest that TTX has a defensive function in adult P. maculata, who then invest this in their progeny for protection. Localization in the digestive tissue of P. maculata potentially indicates a dietary source of TTX. Stylochoplana sp. may use TTX in prey capture and for the protection of offspring

A Two-Step Synthesis of Avobenzone.

Avobenzone is an important agent in sunscreen that reacts with the full spectrum of UVA/UVB light. In fact, avobenzone has one of the largest UV light absorbance ranges of all sunscreen agents. The wide absorbance range of avobenzone helps the sunscreen better protect the skin. This project involved two steps to synthesize avobenzone. Starting with 4-tert-butylbenzaldehyde, 4-methoxyacetophenone, and a base, an Aldol reaction was used to create a ketol intermediate. This step involved experimentation with several bases, including sodium hydroxide and potassium-tert-butoxide, to attempt to stop the product at this intermediate ketol form. Two different mixing methods were also compared in the synthesis of this ketol intermediate. The second step involved conversion of the ketol to the diketone avobenzone product after combination with an oxidizing agent. To make this synthesis more green, a one-step synthesis relying on a Claisen reaction was also attempted

Discovery of low-metallicity stars in the central parsec of the Milky Way

We present a metallicity analysis of 83 late-type giants within the central 1 pc of the Milky Way. K-band spectroscopy of these stars were obtained with the medium-spectral resolution integral-field spectrograph NIFS on Gemini North using laser-guide star adaptive optics. Using spectral template fitting with the MARCS synthetic spectral grid, we find that there is large variation in metallicity, with stars ranging from [M/H] $<$ -1.0 to above solar metallicity. About 6\% of the stars have [M/H] $<$ -0.5. This result is in contrast to previous observations, with smaller samples, that show stars at the Galactic center have approximately solar metallicity with only small variations. Our current measurement uncertainties are dominated by systematics in the model, especially at [M/H] $>$ 0, where there are stellar lines not represented in the model. However, the conclusion that there are low metallicity stars, as well as large variations in metallicity is robust. The metallicity may be an indicator of the origin of these stars. The low-metallicity population is consistent with that of globular clusters in the Milky Way, but their small fraction likely means that globular cluster infall is not the dominant mechanism for forming the Milky Way nuclear star cluster. The majority of stars are at or above solar metallicity, which suggests they were formed closer to the Galactic center or from the disk. In addition, our results indicate that it will be important for star formation history analyses using red giants at the Galactic center to consider the effect of varying metallicity.Comment: 11 pages, 10 figures, ApJ Accepte

Investigation of a pulsed electrothermal thruster system

The performance of an ablative wall Pulsed Electrothermal (PET) thruster is accurately characterized on a calibrated thrust stand, using polyethylene propellant. The thruster is tested for four configurations of capillary length and pulse length. The exhaust velocity is determined with twin time-of-flight photodiode stagnation probes, and the ablated mass is measured from the loss over ten shots. Based on the measured thrust impulse and the ablated mass, the specific impulse varies from 1000 to 1750 seconds. The thrust to power varies from .05 N/kW (quasi-steady mode) to .10 N/kW (unsteady mode). The thruster efficiency varies from .56 at 1000 seconds to .42 at 1750 seconds. A conceptual design is presented for a 40 kW PET propulsion system. The point design system performance is .62 system efficiency at 1000 seconds specific impulse. The system's reliability is enhanced by incorporating 20, 20 kW thruster modules which are fired in pairs. The thruster design is non-ablative, and uses water propellant, from a central storage tank, injected through the cathode

Response of Amphibian and Invertebrate Communities to Wetland Mitigation in the Greater Yellowstone Ecosystem

In the United States, a “no net loss” of wetlands policy mandates that when wetland impacts cannot be avoided, they must be mitigated by creating or restoring wetlands of equal or greater area. A primary goal of these projects is often habitat replacement, but success is generally evaluated only through presence of wetland-associated vegetation and physical characteristics, which may not be good surrogates for wetland function. Because amphibians and aquatic macroinvertebrates integrate processes at multiple levels and are sensitive to conditions in both the aquatic and surrounding terrestrial environment, evaluating their response to wetland mitigation may be more meaningful. The Wyoming Department of Transportation recently (2008-2013) constructed and restored 38 wetlands in Teton County, WY to mitigate for loss of wetland area caused by a road reconstruction project. Our objectives were to assess differences in species richness and community composition of amphibian and aquatic macroinvertebrate communities among ten constructed, seven impacted and ten reference wetlands. Preliminary results suggest that amphibians and invertebrates have quickly colonized created wetlands, leading to similar species richness among wetland types, but that community composition remains distinct even several years after wetland construction. These results suggest that wetland creation may be an important tool, but that the life histories of target species should be accounted for in the design phase to maximize the probability of native amphibian and invertebrate colonization and persistence