Modulation of swimming in the gastropod Melibe leonina by nitric oxide

Nitric oxide (NO) is a gaseous intercellular messenger produced by the enzyme nitric oxide synthase. It has been implicated as a neuromodulator in several groups of animals, including gastropods, crustaceans and mammals. In this study, we investigated the effects of NO on the swim motor program produced by isolated brains and by semi-intact preparations of the nudibranch Melibe leonina. The NO donors sodium nitroprusside (SNP, 1 mmol l–1) and S-nitroso-N-acetylpenicillamine (SNAP, 1 mmol l–1) both had a marked effect on the swim motor program expressed in isolated brains, causing an increase in the period of the swim cycle and a more erratic swim rhythm. In semi-intact preparations, the effect of NO donors was manifested as a significant decrease in the rate of actual swimming. An NO scavenger, reduced oxyhemoglobin, eliminated the effects of NO donors on isolated brains, supporting the assumption that the changes in swimming induced by donors were actually due to NO. The cGMP analogue 8-bromoguanosine 3′,5′-cyclic monophosphate (1 mmol l–1) produced effects that mimicked those of NO donors, suggesting that NO is working via a cGMP-dependent mechanism. These results, in combination with previous histological studies indicating the endogenous presence of nitric oxide synthase, suggest that NO is used in the central nervous system of Melibe leonina to modulate swimming

Neural Correlates of Swimming Behavior in Melibe leonina

The nudibranch Melibe leonina swims by rhythmically bending from side to side at a frequency of 1 cycle every 2–4 s. The objective of this study was to locate putative swim motoneurons (pSMNs) that drive these lateral flexions and determine if swimming in this species is produced by a swim central pattern generator (sCPG). In the first set of experiments, intracellular recordings were obtained from pSMNs in semi-intact, swimming animals. About 10–14 pSMNs were identified on the dorsal surface of each pedal ganglion and 4–7 on the ventral side. In general, the pSMNs in a given pedal ganglion fired synchronously and caused the animal to flex in that direction, whereas the pSMNs in the opposite pedal ganglion fired in anti-phase. When swimming stopped, so did rhythmic pSMN bursting; when swimming commenced, pSMNs resumed bursting. In the second series of experiments, intracellular recordings were obtained from pSMNs in isolated brains that spontaneously expressed the swim motor program. The pattern of activity recorded from pSMNs in isolated brains was very similar to the bursting pattern obtained from the same pSMNs in semi-intact animals, indicating that the sCPG can produce the swim rhythm in the absence of sensory feedback. Exposing the brain to light or cutting the pedal-pedal connectives inhibited fictive swimming in the isolated brain. The pSMNs do not appear to participate in the sCPG. Rather, they received rhythmic excitatory and inhibitory synaptic input from interneurons that probably comprise the sCPG circuit

The Hohfeldian Approach to Constitutional Cases

INFERRED, OR AT THE MOST rebuttably presumed, is a slight acquaintanceship on the part of the reader with the work on jural opposites and jural correlatives by Professor W. Newcomb Hohfeld. The Founding Fathers, as though anticipating the coming of the Messianic logician, used all of the four Hohfeldian gravamen terms-rights, privileges, powers and immunities-in the Constitution of the United States,\u27 and for this reason the author perceives a nexus between Hohfeldian logic and constitutional construction. The appropriate initial touchstone for contemporary use of this theory could appear to be the 1968 case of Flast v. Cohen, considering Mr. Justice Harlan\u27s allusions to Hohfeld in his dissenting opinion

A Commentary on Hegelian Philosophy and the Absolutes in Law

The principles of law are twofold: those that are absolute and those that are relative. The absolute and the relative are akin to dogma and doctrine, respectively. We are on shaky ground indeed when we stand upon relativism. The principal purveyors of relativism have been Justices Cardozo, Douglas, and Holmes

Alien Registration- Newcomb, Richard H. (Leeds, Androscoggin County)

https://digitalmaine.com/alien_docs/26818/thumbnail.jp

The Legal and Political Foundations and Meaning of President Wilson\u27s Great Western Tour

September 4, 1919 is a red-letter date in history. On that date President Woodrow Wilson, wearing a sailor straw hat after Labor Day revealed his famous smile when he arrived in Columbus, Ohio. There, he delivered the first of forty-two speeches which concluded on September 25, in Pueblo, Colorado. Those twenty-two days marked the most memorable train trip in history - President Wilson\u27s Great Western Tour: a journey through sixteen states aboard the special seven-car Presidential train, the Mayflower. The train was aptly named, for the President\u27s speaking tour symbolized the hope of the world, just as the Pilgrims\u27 hope led them to set forth for the New World hundreds of years before

Detection of Salinity by the Lobster, Homarus americanus

Changes in the heart rates of lobsters (Homarus americanus) were used as an indicator that the animals were capable of sensing a reduction in the salinity of the ambient seawater. The typical response to a gradual (1 to 2 ppt/min) reduction in salinity consisted of a rapid increase in heart rate at a mean threshold of 26.6 ± 0.7 ppt, followed by a reduction in heart rate when the salinity reached 22.1 ± 0.5 ppt. Animals with lesioned cardioregulatory nerves did not exhibit a cardiac response to changes in salinity. A cardiac response was elicited from lobsters exposed to isotonic chloride-free salines but not to isotonic sodium-, magnesium- or calcium-free salines. There was little change in the blood osmolarity of lobsters when bradycardia occurred, suggesting that the receptors involved are external. Furthermore, lobsters without antennae, antennules, or legs showed typical cardiac responses to low salinity, indicating the receptors are not located in these areas. Lobsters exposed to reductions in the salinity of the ambient seawater while both branchial chambers were perfused with full-strength seawater did not display a cardiac response until the external salinity reached 21.6 ± 1.8 ppt. In contrast, when their branchial chambers were exposed to reductions in salinity while the external salinity was maintained at normal levels, changes in heart rate were rapidly elicited in response to very small reductions in salinity (down to 29.5 ± 0.9 ppt in the branchial chamber and 31.5 ± 0.3 ppt externally). We conclude that the primary receptors responsible for detecting reductions in salinity in H. americanus are located within or near the branchial chambers and are primarily sensitive to chloride ions

An approximation scheme for an Eikonal Equation with discontinuous coefficient

We consider the stationary Hamilton-Jacobi equation where the dynamics can vanish at some points, the cost function is strictly positive and is allowed to be discontinuous. More precisely, we consider special class of discontinuities for which the notion of viscosity solution is well-suited. We propose a semi-Lagrangian scheme for the numerical approximation of the viscosity solution in the sense of Ishii and we study its properties. We also prove an a-priori error estimate for the scheme in an integral norm. The last section contains some applications to control and image processing problems