The myth of nitric oxide in central cardiovascular control by the nucleus tractus solitarii

Considerable evidence suggests that nitroxidergic mechanisms in the nucleus tractus solitarii (NTS) participate in cardiovascular reflex control. Much of that evidence, being based on responses to nitric oxide precursors or inhibitors of nitric oxide synthesis, has been indirect and circumstantial. We sought to directly determine cardiovascular responses to nitric oxide donors microinjected into the NTS and to determine if traditional receptor mechanisms might account for responses to certain of these donors in the central nervous system. Anesthetized adult Sprague Dawley rats that were instrumented for recording arterial pressure and heart rate were used in the physiological studies. Microinjection of nitric oxide itself into the NTS did not produce any cardiovascular responses and injection of sodium nitroprusside elicited minimal depressor responses. The S-nitrosothiols, S-nitrosoglutathione (GSNO), S-nitrosoacetylpenicillamine (SNAP), and S-nitroso-D-cysteine (D-SNC) produced no significant cardiovascular responses while injection of S-nitroso-L-cysteine (L-SNC) elicited brisk, dose-dependent depressor and bradycardic responses. In contrast, injection of glyceryl trinitrate elicited minimal pressor responses without associated changes in heart rate. It is unlikely that the responses to L-SNC were dependent on release of nitric oxide in that 1) the responses were not affected by injection of oxyhemoglobin or an inhibitor of nitric oxide synthesis prior to injection of L-SNC and 2) L- and D-SNC released identical amounts of nitric oxide when exposed to brain tissue homogenates. Although GSNO did not independently affect blood pressure, its injection attenuated responses to subsequent injection of L-SNC. Furthermore, radioligand binding studies suggested that in rat brain synaptosomes there is a saturable binding site for GSNO that is displaced from that site by L-SNC. The studies suggest that S-nitrosocysteine, not nitric oxide, may be an interneuronal messenger for cardiovascular neurons in the NTS

Protective Effect of Aortic Stenosis on the Coronary Arteries. Hypothetic Considerations to an Old Enigma

Abstract A literature overview of angiographic studies has shown that the prevalence of significant coronary disease in patients with aortic stenosis (AS) varies from 20 to 60%. Early necropsy studies suggested that patients with AS had a lower than expected incidence of coronary artery disease (CAD), originating the concept of a protective effect of AS on the coronary arteries. The myth of AS protection against CAD would be better explained as endothelium-myocardial interaction (crosstalk) protection triggered by left ventricular overload. Therefore, the cGMP/NO pathway induced by the AS overload pressure would explain the low incidence of CAD, which is compatible with the amazing natural long-term evolution of this cardiac valve disease.

O mito do populismo econômico de Vargas

The myth of Vargas' economic populism. The Second Vargas Administration in Brazil (1951-1954) is commonly associated with the phenomenon of populism. However, based on the models of economic populism, it is clear that the economic policy of the period is not the one shown by those models. Besides, based on this historic experience, it is advocated that there is no incompatibility between developmentalism and the adoption of macroeconomic stability-oriented measures.

Of empty thoughts and blind intuitions Kant's answer to McDowell

This paper examines the relation between intuition and concept in Kant in light of John McDowell's neo-Kantian position that intuitions are concept-laden.2 The focus is on Kant's twofold pronouncement that thoughts without content are empty and that intuitions without concepts are blind. I show that intuitions as singular representations are not instances of passive data intake but the result of synthetic unification of the given manifold of the senses by the power of the imagination under the guidance of the understanding. Against McDowell I argue that the amenability of intuitions to conceptual determination is not due some pre-existing, absolute conceptuality of the real but to the "work of the subject."3 On a more programmatic level, this paper seeks to demonstrate the limitations of a selective appropriation of Kant and the philosophical potential of a more comprehensive and thorough consideration of his work. Section 1 addresses the unique balance in Kant's philosophy between the work on particular problems and the orientation toward a systematic whole. Section 2 outlines McDowell's take on the Kantian distinction between intuition and concept in the context of the Kant readings by Sellars and Strawson. Section 3 exposes McDowell's relapse into the Myth of the Given. Section 4 proposes a reading of Kant's theoretical philosophy as an epistemology of metaphysical cognition. Section 5 details Kant's original account of sensible intuition in the Inaugural-Dissertation of 1770. Section 6 presents the transition from the manifold of the senses to the synthesis in the imagination and the unification through the categories in the Critique of pure reason (1781 and 1787). Section 7 addresses Kant's formalism in epistemology and metaphysics.