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ENKEPHALIN MODULATION OF NEURAL TRANSMISSION IN THE CAT STELLATE GANGLION - PHARMACOLOGICAL ACTIONS OF EXOGENOUS OPIATES
No full textNeural ganglionic transmission was studied in vivo in the cat, using closed chest anesthetized preparations. The right stellate ganglion and its branches were exposed retropleurally and prepared for electrical stimulation of pre- and postganglionic nerve fibers. The axillary artery was cannulated allowing direct administration of drugs in the arterial blood supplying the ganglion. Stimulation of postjunctional receptors could thus be obtained by local administration of selective agents. Local administration of nicotinic, muscarinic or histaminergic agents increased heart rate and blood pressure. Opiates were given either i.v. or locally through the axillary artery: we tested the effects of morphine, Leu-enkephalin (Leu-enk), Met-enkephalin (Met-enk), [d-ala2]-Met-enkephalinamide (DAME) and etorphine. When given locally, Leu-enk (from 10 μg). Met-enk (from 20 μg), DAME (from 5 μg) and etorphine (from 0.2 μg) inhibited tachycardia induced by preganglionic stimulation and reduced the amplitude of the compound action potential recorded from the postganglionic nerve. Morphine (10-200 μg) had no effect. On the other hand, tachycardia induced by postganglionic nerve stimulation was unaffected by opiates in the same experimental conditions. Intravenous administration of similar doses of opiates had no effect on ganglionic transmission. When tachycardia was induced by chemical stimulation of nicotinic (DMPP), muscarinic (McN-A-343-1 l) or histamine receptors in the stellate ganglia, opiates were still active in reducing the effect of these chemicals. These data provide evidence that exogenous opiates exert a depressing action on postsynaptic responses of sympathetic ganglia tested in vivo, although an additional action on presynaptic terminals is not excluded. As endogenous opiates are normally present in various sympathetic ganglia, including the stellate ganglion of the cat, it is possible that they play some modulatory role on ganglionic transmission in physiological conditions
Muscle reinnervation—I. Restoration of transmitter release mechanisms
No full textFollowing sciatic nerve crush the restoration of neuromuscular transmission in the extensor digitorum longus muscle of rat proceeds in a well defined manner: 1. (a) as soon as the nerve-muscle contact is reformed, a subthreshold end-plate potential is recorded; no 'non-transmitting stage' is observed; 2. (b) 24hours later muscle action potentials are induced by nerve stimulation; 3. (c) miniature end-plate potentials are absent or very rare at the newly reinnervated end-plates; their frequency returns to normal in about 4 weeks; 4. (d) the frequency is also very much reduced in 30 mM K+ and hypertonic solutions and recovers slowly, in 4 and 5 weeks, respectively, while black widow spider venom is from the beginning as powerful as in normal neuromuscular junctions; 5. (e) at the early stages of reinnervation the Ca2+-dependent release mechanisms are much stronger than control cases, while the Ca2+-independent mechanisms are weaker and recover in 5 weeks. The gradual reassembly and restoration of neurotransmitter release mechanisms of the extensor digitorum longus nerve terminal indicate the complexity of pre-synaptic ending organization
THE ACTION OF AD6 ON EXPERIMENTAL ARRHYTHMIAS AND ON ACTION-POTENTIALS OF CARDIAC FIBERS
No full textMotor nerve sprouting induced by ganglioside treatment. Possible implications for gangliosides on neuronal growth
No full textMuscle reinnervation—II. Sprouting, synapse formation and repression
No full textExtensor digitorum longus muscle is reinnervated by the regenerating neurites at the endplate region; as soon as the contact is made, the rate of neurite elongation inside the cleft decreases about 1000-fold while interfibre growth and sprout formation proceed unchanged.
Polyinnervation reaches the maximum level 7–10 days after reinnervation, then synaptic repression begins. The elimination of redundant innervation takes place when the biophysical properties of the muscle are again normal. There is no sign of either phagocytosis or degeneration, therefore the process of synaptic repression is probably due to retraction, as neurites do when in culture.
The role of Schwann cells and nerve sheath in the process of maintenance is suggested
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
PGF2-ALPHA THROMBOXANE-B2 AND HETE LEVELS IN GERBIL BRAIN CORTEX AFTER LIGATION OF COMMON CAROTID ARTERIES AND DECAPITATION
No full textThe effects of ligation of both common carotid arteries in the gerbil on the levels of PGF2α, TXB2, HETE and of energy metabolites in brain cortex, have been investigated. Also, in the same experimental conditions the changes of cyclic AMP in brain cortex, cerebellum, striatum and hippocampus have been monitored. ATP, glycogen, glucose and phosphocreatine decrease whereas, lactate and cyclic AMP are enhanced in the ischemic brain, as previously reported. In contrast, levels of arachidonic acid metabolites are not modified. During ischemia following decapitation, instead, PGF2α, and TXB2, show considerable increase
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