Pressure physiology

Shock is a clinical syndrome in which profound and widespread reduction in the effective delivery of oxygen and other nutrients to the tissues. In shock condition, the individual is weak, anxious with coldness of extremeties, sweeting and marked fall in arterial pressure. Physiologic mechanisms can effect the arterial pressure by acting on one or more of two variables i.e. preload, impedance to blood flow (after load) and myocardral contractility. These macha-nisms include ... 

Cunningham AJ, Barry P. Intraocular pressure—physiology and implications for anaesthetic management. Can Anaesth Soc J 1986 33(2) 195-208. 

The physiological and biochemical effects of the atmospheric inert gases should not be excluded from consideration in high pressure physiology studies. 

Baraeh AL, GJ Beek. Exsufflation with negative pressure physiologic and clinical studies in poliomyelitis, bronehial asthma, pulmonary emphysema and bronchiectasis. Arch Intern Med 1954 93(6) 825-841. 

Physiological responses to prostaglandins encompass a variety of effects Some prostaglandins relax bronchial muscle others contract it Some stimulate uterine con tractions and have been used to induce therapeutic abortions PGEj dilates blood vessels and lowers blood pressure it inhibits the aggregation of platelets and offers promise as a drug to reduce the formation of blood clots... 

Until separation techniques such as chromatography (28,29) and counter-current extraction had advanced sufficientiy to be of widespread use, the principal alkaloids were isolated from plant extracts and the minor constituents were either discarded or remained uninvestigated. With the advent of, first, column, then preparative thin layer, and now high pressure Hquid chromatography, even very low concentrations of materials of physiological significance can be obtained in commercial quantities. The alkaloid leurocristine (vincristine, 22, R = CHO), one of the more than 90 alkaloids found in Catharanthus roseus G. Don, from which it is isolated and then used in chemotherapy, occurs in concentrations of about 2 mg/100 kg of plant material. 

Human evolution has taken place close to sea level, and humans are physiologically adjusted to the absolute partial pressure of the oxygen at that point, namely 21.2 kPa (159.2 mm Hg), ie, 20.946% of 101.325 kPa (760 mm Hg). However, humans may become acclimatized to life and work at altitudes as high as 2500—4000 m. At the 3000-m level, the atmospheric pressure drops to 70 kPa (523 mm Hg) and the oxygen partial pressure to 14.61 kPa (110 mm Hg), only slightly above the 13.73 kPa (102.9 mm Hg) for the normal oxygen pressure in alveolar air. To compensate, the individual is forced to breathe much more rapidly to increase the ratio of new air to old in the lung mixture. 

Dihydropyridines not only are intermediates for the synthesis of pyridines, but also are themselves an important class of N-heterocycles an example is the coenzyme NADH. Studies on the function of NADH led to increased interest in the synthesis of dihydropyridines as model compounds. Aryl-substituted dihy-dropyridines have been shown to be physiologically active as calcium antagonists. Some derivatives have found application in the therapy of high blood pressure and angina pectoris. For that reason the synthesis of 1,4-dihydropyridines has been the subject of intensive research and industrial use. The Hantzsch synthesis has thus become an important reaction. 

Epinephrine itself does find some use in clinical medicine. The drug is used in order to increase blood pressure in cases of circulatory collapse, and to relax the bronchial muscle in acute asthma and in anaphylactic reactions. These activities follow directly from the agent s physiologic role. The biogenetic precursor of epinephrine, norepinephrine, has activity in its own right as a mediator of sympathetic nerve action. (An apocryphal story has it that the term nor is derived from a label seen on a bottle of a key primary amine in a laboratory in Germany N ohne... 

It is the almost universal practice to record the nature and strength of an odour at the particular temperature which may obtain at the time of examination. Substances at their temperatures of boiling have a common vapour pressure equal to that of the atmosphere, but it is clearly impossible to smell a substance in such a condition, whereas, if we could go to the other extreme, the absolute zero, it is probable that no vapour would exist as such and for this reason alone, apart from any physiological one, no odour would be discernible. 

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