Chronic hypoxia: evidence for parasympathetic stimulation and cGMP/cAMP-mediated DNA synthesis.
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Biomedical subjects
Publications and source records attributed to W Beier.
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In anesthetized, spontaneously breathing rabbits, intratracheally administered isotonic saline, acetylcholine (Ach) and histamine (His) induced an increase of airway resistance up to 183, 571, and 312%, respectively, compared with untreated controls. This was accompanied by a decrease of the arterial pO2. Bilateral cervical vagotomy led to nearly complete inhibition of the saline- and Ach-induced bronchoconstriction, whereas the His effect was only reduced to 202%. Vagotomy did not improve the arterial pO2. While the bronchoconstrictive effects of isotonic saline and Ach revealed a significant linear correlation with the increased cGMP/cAMP ratio, His did not cause an alteration of the cGMP/cAMP ratio to a degree that corresponds to its bronchoconstrictive activity. These data indicate that (1) bronchoconstriction-inducing agents may act (a) by stimulation of the parasympathetic nerve or (b) by contracting smooth muscles directly; (2) alveolar ventilation is not regulated by the parasympathetic nerve, and (3) bronchoconstriction induced by parasympathetic stimulation is associated with or mediated by an increase of the cGMP/cAMP ratio.
In the view of theoretical considerations the human course of life is regarded as a generalized motion. It is made an attempt to define terms, such as chronological age, biological age and ageing. In the model of ageing irreversible alterations affecting the organism are described by a complex variable, called vitality, which represents the state of systems. The rate of vitality dV/dt and the biomorphosis of systems are equivalent terms.
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